Qmail, Mail toaster
What is a mail toaster, and what are we doing here?
A "mail toaster" is a silly name for a very useful and commonly needed "applicance" - a single server that can handle everything you need to do with email: receive it, send it, weed out spam, allow webmail access, allow authenticated SMTP traffic so that laptop users and other "road warriors" can send email from any network they happen to be attached to, handle multiple mail domains, allow delegation of web-based administration of individual domains to individuals responsible for those domains (and their domain only), and even allow delegation of web-based individual mailbox maintenance to owners of the individual mailboxes.
When you're done following through this article, you'll have a machine which will do exactly that - and even a few things more, like allow users to set "auto-reply" messages, forward their mail temporarily to other addresses, you name it.
We'll be using the following ports:
First of all, you're going to need a FreeBSD server - all of the applications we're going to use are free software and available for pretty much any *nix, but we're going to be covering installing them using the ports tree... so your mileage would vary considerably were you to be trying to follow this article along on a Linux or Solaris or what have you.
Second of all, you're going to need DNS information set up to point the mail services (MX records) for any domains that you want to handle mail for at this machine. You may or may not want the same server to act as nameserver (DNS server) and mailserver, but either way, setting up DNS is beyond the scope of this article... we're just going to set up the services themselves here, not set up the internet to point the mail at us to begin with.
Finally, before we get started, be sure to synchronize your ports tree to make sure you get the newest versions of all the ports you'll be installing. Mailserver components are critical, you don't want to wind up with something outdated that could potentially have had a vulnerability disclosed in it!
ph34r# cvsup /usr/share/examples/cvsup/ports-supfile
And now that we have the latest versions of all of our ports, let's get started!
This is probably the easiest part of the whole process. Note: if you've already got your own copy of Apache up and running and you know how to care for it and feed it, that's perfectly fine, and you can skip on ahead to the next section - we aren't really going to do a whole lot of magical things with the webserver, we just need it available so that we can deliver our webmail and web-based control interfaces. It's also fine if you're using Apache 1.x instead of Apache 2.x; just make your own little adjustments and follow right along.
ph34r# cd /usr/ports/www/apache2 ph34r# make install clean
When the port's done building, rehash to update your system's PATH cache, and start Apache:
ph34r# rehash ph34r# apachectl start
Check to make sure it's running:
ph34r# ps ax | grep httpd 91237 ?? Ss 0:00.37 /usr/local/sbin/httpd -k start 91246 ?? S 0:00.00 /usr/local/sbin/httpd -k start 91247 ?? S 0:00.00 /usr/local/sbin/httpd -k start 91248 ?? S 0:00.00 /usr/local/sbin/httpd -k start 91249 ?? S 0:00.00 /usr/local/sbin/httpd -k start 91250 ?? S 0:00.00 /usr/local/sbin/httpd -k start
And we're good! Now, on to the parts that actually handle the mail...
Installing Qmail with SMTP Authentication
Now, it's time to get the basics installed - first things first, get Qmail installed with the SMTP_AUTH and the TLS patches in place. This will allow us not only to send and receive mail, but also to authenticate SMTP sessions with a username and password so that authorized "road warriors" can use this server to send their email no matter what network they are physically attached to, and to use TLS encryption if supported on the remote end (which might be one of those road warriors, or might be another domain's mailserver) to keep potential unfriendlies from easily sniffing potentially sensitive information out of our email.
Note that we're NOT issuing make install clean as a single command here, because there are other steps we want to take after building the port before we clean out the work directory!
ph34r# cd /usr/ports/mail/qmail-smtp_auth+tls ph34r# make enable-qmail
Making or Requesting a Certificate for Qmail's TLS
Now we'll need to install a certificate for use with TLS authentication/encryption. To make a certificate request, you can type in make certificate-req - but that's all I can tell you about that process; I typically use a self-signed certificate instead (one which is not stored at Thawte or Verisign or one of the other major providers, but only on the local server). You don't have to pay for a self-signed certificate, where you would for one from Thawte or Verisign et al, but you should be aware that 1. users will be warned that they are being asked to accept a certificate not signed by a recognized authority the first time they connect to a server with a self-signed certificate, and 2. Microsoft Outlook may refuse to connect to a server with a self-signed certificate using TLS AT ALL, so you may need to forgo encryption entirely for Outlook users if you're signing your own certificate.
Whew! With that said, actually generating the certificate is easy:
ph34r# make certificate
After entering in a bit of info at some prompts - country, state, city, that sort of thing - a certificate will be created and saved in /var/qmail/control/servercert.pem. All done. One thing worth noting - whatever you enter at the prompt that says Common Name (eg, YOUR name) : is what's going to show up in security prompts in browsers and email clients, and frequently will trigger EXTRA "oh no something's not right!" prompting if it doesn't match the URL of your server. So in general, if you were creating this certificate for a mailserver mail.getsdeliveredhere.net, you would want to enter mail.getsdeliveredhere.net at that prompt.
Initial Qmail Configuration
Now it's time to make sure Qmail knows how to deliver the mail it receives. The way we do this is by selecting one of a large selection of possible startup scripts from /var/qmail/boot, and copying that script to /var/qmail/rc, which is symlinked to /usr/local/etc/rc.d/qmail.sh for starting and stopping Qmail when needed. We're going to be using the maildir storage format, so this is the command we'll issue:
ph34r# cp /var/qmail/boot/maildir /var/qmail/rc
Now we'll need to generate Qmail's basic control files. Easy:
ph34r# /var/qmail/configure/config-fast Your fully qualified host name is . Putting into control/me... Putting into control/defaultdomain... Putting into control/plusdomain... Putting into control/locals... Putting into control/rcpthosts... Now qmail will refuse to accept SMTP messages except to . Make sure to change rcpthosts if you add hosts to locals or virtualdomains! ph34r#
Now you need to put the real name of the machine in /var/qmail/control/me - nothing fancy here, no comments, no arguments to set, just edit the file and put the name of the server in there; ie mail.getsdeliveredhere.net. Don't worry about locals, rcpthosts, or any of that good stuff - vpopmail will handle that for us, and we're going to cover that next. But first, we need to fire up qmail and make sure it's running:
ph34r# /usr/local/etc/rc.d/qmail.sh start ph34r# ps ax | grep qmail 87877 p0 R 0:00.26 qmail-send 87878 p0 S 0:00.10 splogger qmail 87879 p0 S 0:00.00 qmail-lspawn ./Maildir/ 87880 p0 S 0:00.03 qmail-rspawn 87881 p0 S 0:00.03 qmail-clean
Good deal! Now on to vpopmail.
Now, we want to make sure that we can keep our mail accounts separate from our system accounts - maybe you want every Tom, Dick, and Harry with an email account to potentially be able to use that username and password to get a shell prompt, but I certainly don't! In fact, even for those folks - like myself - who have both a mailbox and a shell account, I want to make certain that the credentials used AREN'T the same, to minimize security risks. I also want to make it easy to administer the email for multiple domains from a single machine - and that's where vpopmail comes in.
ph34r# cd /usr/ports/mail/vpopmail ph34r# make install clean
Now we need to make a quick permissions change, so that our authenticated SMTP will work right with Vpopmail's password authentication program:
ph34r# chmod 4755 /usr/local/vpopmail/bin/vchkpw ph34r# chown root /usr/local/vpopmail/bin/vchkpw
Mmmmm, simple. That's all we have to do with vpopmail. As a bonus, installing vpopmail also got us the ucspi-tcp port, which we'll need to use to keep a daemon listening on port 25 (and port 2525, for reasons we'll discuss later) for incoming SMTP traffic. Okay, but now that we've got a separate database for mailbox accounts from system accounts, how do we manage it? That would be two more ports - qmailadmin, and vqadmin. Vqadmin lets us add, delete, and otherwise manage entire domains we want to handle the mail for, while qmailadmin gives us a nice friendly little interface to handle individual mailboxes within individual domains. First, vqadmin:
ph34r# cd /usr/ports/mail/vqadmin ph34r# make install clean
Now, the vqadmin port just put its files in /usr/local/www/cgi-bin-dist/vqadmin and /usr/local/www/data-dist/images. This is probably NOT where you actually want those files to go - so you'll want to move that whole directory to wherever you actually want it served from. For the purposes of this article, we'll assume that it's a mailserver and a mailserver only, and so you're just serving everything from /usr/local/www/data and /usr/local/www/cgi-bin. So we'll move the files where we need them:
ph34r# mv /usr/local/www/cgi-bin-dist/vqadmin /usr/local/www/cgi-bin ph34r# mv /usr/local/www/data-dist/images /usr/local/www/data
Now we'll need to add a snippet to our httpd.conf file to handle authentication for us when we use vqadmin:
# VQadmin : web interface for administering Qmail <Directory "/usr/local/www/cgi-bin/vqadmin"> deny from all Options ExecCGI AllowOverride AuthConfig Order deny,allow </Directory>
All that does is make sure that access is allowed to our vqadmin directory, but ONLY allowed for authorized users. Next, we'll need to create a .htaccess file and a password file to tell the system what does or does not constitute an authorized user. First, create the .htaccess file in the directory you put vqadmin in (in this example /usr/local/www/cgi-bin/vqadmin):
# This is /usr/local/www/cgi-bin/vqadmin/.htaccess AuthType Basic AuthUserFile /usr/local/www/vqadmin.passwd AuthName vQadmin require valid-user satisfy any
Now, it's time to create the password file referenced in the .htaccess file you just wrote. In this example, we're going to use the username "admin" because it's already configured in vqadmin's vqadmin.acl file to be an administrator account when present - REMEMBER, if instead you choose to use a different username, and you want that username to be able to administer vqadmin as well as look at it, you'll need to edit vqadmin.acl as well to reflect that!
ph34r# htpasswd -c /usr/local/www/vqadmin.passwd admin New password: Re-type new password: Adding password for user admin
The htpasswd command, with the -c flag, will create the new file and will add the user "admin", with the password you specify twice on the command line when prompted. The screen will not echo your keystrokes or any asterisks; it will just sit there until you hit enter at each password prompt.
Okay! Now you should be ready to add your first (possibly your only) domain, using vqadmin. First, restart Apache so that the changes you made to httpd.conf will take effect:
ph34r# apachectl restart
Now fire up your web browser and check out your particular version of "www.yourdomainname.tld/cgi-bin/vqadmin/vqadmin.cgi". You should get a plain-but-functional HTML page showing you links to add/delete/otherwise maintain your domains. Add a domain here, and let's move on to qmailadmin.
VQadmin handles the overall installation / deleting / privilege editing of entire domains from the system administrator's level, and it can even be used for modifying individual mailboxes, in a primitive kind of way. But for actually maintaining existing domains - and just as importantly, for delegating the handling of individual domains and individual mailboxes in those domains to the people who actually use them - what we want is Qmailadmin. First, we'll build it from the ports tree:
ph34r# cd /usr/ports/mail/qmailadmin ph34r# make install clean
Qmailadmin dumps its files in /usr/local/www/cgi-bin.default and /usr/local/www/data.default, which is certainly not where we actually want them. Again, we'll want to put them in the correct cgi-bin directory for whatever your webserver configuration is - in our example, it looks like this:
ph34r# mv /usr/local/www/cgi-bin.default/qmailadmin /usr/local/www/cgi-bin ph34r# mv /usr/local/www/data.default/qmailadmin /usr/local/www/data
Now the nice thing is, since Qmailadmin uses the actual mailbox usernames and passwords themselves to authenticate, you don't have to futz about any with .htaccess files and password files like VQadmin needed - once you've copied those files, you're good to go!
Go ahead and test it out by browsing to www.yourdomainname.tld/cgi-bin/qmailadmin/qmailadmin. You should get a nice little login screen asking for a username and password and domain. Remember the domain you added when you tested VQadmin earlier? Log in here as username postmaster, password whatever you set when you created the domain, and domain name as whatever domain name you created earlier. Voila! You're set up, and you can add/delete/manage/mangle mailboxes and mailing lists and what have you in this domain to your heart's content.
You can also set the postmaster password to this domain to be DIFFERENT from the password to access VQadmin, and delegate this domain's administration to someone else without worrying about them getting into something on another domain you're hosting mail for. You can even let owners of individual mailboxes login as themselves, and they'll be able to change the settings for their own mailbox, but not for others on the domain or anything domain-wide. Handy!
If you have to spend much time working on other people's computers, you'll probably want to be able to use a web interface to check your email as well as administer your server. For that, we use sqwebmail - which is the webmail chunk of the Courier mailserver package, by itself. Sqwebmail assumes a maildir storage format, and it's blindingly fast compared to most other webmail packages because it does not use IMAP to communicate with the actual server - it just accesses the maildirs directly.
When we install, we'll be using the -DWITH_VCHKPW argument, to set the environment variable "WITH_VCHKPW" to true, so that the port knows we want it to build using Vpopmail authentication routines.
ph34r# cd /usr/ports/mail/sqwebmail ph34r# make -DWITH_VCHKPW ph34r# make install ph34r# make install-configure ph34r# make clean
First, as usual for web-based ports, we have to copy a couple of directories from "where they got put" to "where they should be."
ph34r# mv /usr/local/www/data-dist/sqwebmail /usr/local/www/data ph34r# mv /usr/local/www/cgi-bin-dist/sqwebmail /usr/local/www/cgi-bin
Sqwebmail uses a fairly complex daemon-based method of authentication, so we'll have to futz about with a few config files and make sure the daemons get run, as well:
ph34r# edit /usr/local/etc/rc.d/sqwebmail-authdaemond.sh
Okay, now what you're going to want to do is find this snippet:
if ! PREFIX=$(expr $0 : "\(/.*\)/etc/rc\.d/$(basename $0)\$"); then echo "$0: Cannot determine the PREFIX" >&2 exit 1 fi
And replace it with this one:
Now you'll need to replace the same snippet with the same PREFIX setting in one more file:
ph34r# edit /usr/local/etc/rc.d/sqwebmail-sqwebmaild.sh
Now start the daemons:
ph34r# /usr/local/etc/rc.d/sqwebmail-authdaemond.sh start ph34r# /usr/local/etc/rc.d/sqwebmail-sqwebmaild.sh start
And you should be ready to test it out! Fire up http://www.yourdomainname.tld/cgi-bin/sqwebmail/sqwebmail, and login as firstname.lastname@example.org (the postmaster account @ the domain you created with vqadmin earlier) and use the same password you set for postmaster on that domain. Voila! You've got webmail.
Okay, so now we've got Qmail running, we've got a virtual domain and its postmaster account set up and working using Vqadmin and Qmailadmin... but as of right now, the only way to check that account is via webmail. This is probably not what we want - what we really want is POP3 and/or IMAP access. There are lots of POP3 and IMAP servers available, but I've had (by far!) the best performance results (and least observed discovered vulnerabilities) from the Dovecot package, so that's what we're going to use here.
ph34r# cd /usr/ports/mail/dovecot ph34r# make -DWITH_VPOPMAIL install
Note that we're specifying the WITH_VPOPMAIL option to make sure that Dovecot understands it should be authenticating using the Vpopmail user credentials, not system user credentials. As of the current port version of Dovecot, you actually get an ncurses GUI pop-up when you build the port; so you should make sure to manually check the VPOPMAIL box if you do. DON'T select POSTGRESQL or MYSQL or any of that other stuff - that's for advanced mail installations which use those databases instead of maildirs for delivery, and it's not what we're doing here!
At the end of the port compilation and installation process, it will ask you a couple of questions, to which you'll just answer "yes":
===> Installing for dovecot-0.99.12.1 You need a group "dovecot". Would you like me to create it [y]? y Done. You need a user "dovecot". Would you like me to create it [y]? y Done.
Now you'll need to fix up the dovecot.conf file to properly set Dovecot up to handle your maildirs, and to authenticate users against Vpopmail credentials.
ph34r# cd /usr/local/etc ph34r# cp dovecot.conf.sample dovecot.conf ph34r# edit dovecot.conf
First, look for the section which configures Dovecot's handling of mail storage. You'll find a bunch of commented-out examples, followed by this NON-commented line:
default_mail_env = mbox:/var/mail/%u
Comment that line out completely - Dovecot will handle maildirs in vpopmail's locations just fine with no config information in dovecot.conf at all, but WON'T handle them properly with that default_mail_env line specified the way it is. So:
#default_mail_env = mbox:/var/mail/%u
Next, find the two lines that look like this (but they won't be together, they will be separated by some comments):
auth_userdb = passwd auth_passdb = passwd
And set them both to read "vpopmail" instead.
auth_userdb = vpopmail auth_passdb = vpopmail
Finally, we'll need to change the valid_uid settings, to make sure that IMAP and POP3 logins are allowed for the vpopmail system account - and (for security reasons) ONLY the vpopmail system account! Look for the appropriate section, and - assuming that your vpopmail installation created your vpopmail system account with the uid of 89, which it should have (and if you're paranoid, cat /etc/passwd | grep vpopmail in another terminal window to check) - change it to read as following:
# Valid UID range for users, defaults to 500 and above. This is mostly # to make sure that users can't log in as daemons or other system users. # Note that denying root logins is hardcoded to dovecot binary and can't # be done even if first_valid_uid is set to 0. first_valid_uid = 89 last_valid_uid = 89
Now we need to set dovecot_enable in /etc/rc.conf:
ph34r# echo dovecot_enable="YES" >> /etc/rc.conf
Now that dovecot's configured, let's fire it up, and make sure it starts:
ph34r# /usr/local/etc/rc.d/dovecot.sh start Starting dovecot. ph34r# ps ax | grep dove 87484 ?? Ss 0:00.00 /usr/local/sbin/dovecot 87485 ?? S 0:00.00 dovecot-auth
Yup - we started it, and the process is running. Now we'll move on to setting up the server to actually listen for incoming SMTP traffic.
Listening for Incoming SMTP
Next, you'll want to get your server actually listening for incoming mail. You'll do that by creating a startup script to run ucspi-tcp listening on port 25 (and port 2525, for reasons we'll get into in a moment) and directing incoming connections to Qmail.
Before we can actually start tcpserver, we need to have a ruleset available to tell it what types of connections to allow from which hosts. This is MANDATORY for setting up SMTP servers, because if you don't disallow mail relay from untrusted networks, spammers will find you VERY VERY QUICKLY and use all your bandwidth irritating lots of people, some of whom will know exactly how to get hold of your ISP and tell them you're a problem child. You Do Not Want This. So, create the following as /etc/tcp.smtp:
Note that this assumes that your server is running on a network 192.168.0.x, which may or may not actually be the case.
Now you'll need to use the tcprules program to compile this into a cdb format ruleset. Rehash to make sure your system's PATH cache knows about tcprules, and let's do it:
ph34r# rehash ph34r# cat /etc/tcp.smtp | tcprules /etc/tcp.smtp.cdb /etc/tcp.smtp.tmp
And finally, we'll need to generate a startup script to run tcpserver with. Some of the lines of the shell script shown below are escaped to multi-line format for readability, and while that should work fine entered as shown, I tend to recommend removing the backslashes and line breaks when you actually enter the script into your own machine, and entering those lines as single continuous lines. One less thing to worry about breaking, right?
So put the following script at /usr/local/etc/rc.d/tcpserver.sh:
#!/bin/sh case "$1" in start) /usr/local/bin/tcpserver -H -l0 -R -c 512 -x /etc/tcp.smtp.cdb -u 82 -g 81 \ 0 smtp /usr/local/bin/rblsmtpd -b -r bl.spamcop.net -r dnsbl.njabl.org \ /var/qmail/bin/qmail-smtpd mail.isreceivedhere.net /usr/local/vpopmail/bin/vchkpw \ /usr/bin/true 2>&1 | /var/qmail/bin/splogger rblsmtpd & /usr/local/bin/tcpserver -H -l0 -R -c 512 -x /etc/tcp.smtp.cdb -u 82 -g 81 \ 0 2525 /usr/local/bin/rblsmtpd -b -r bl.spamcop.net -r dnsbl.njabl.org \ /var/qmail/bin/qmail-smtpd mail.isreceivedhere.net /usr/local/vpopmail/bin/vchkpw \ /usr/bin/true 2>&1 | /var/qmail/bin/splogger rblsmtpd & ## -H tells tcpserver not to do remote DNS lookup before accepting connections ## -l0 tells tcpserver not to look up local host name in DNS; instead use "0" as its name ## -R tells tcpserver not to ask the remote server for its DNS information ## -c 512 tells tcpserver not to attempt to process more than 512 simultaneous connections ## -x specifies a rules database to control connections with ## -u 82 runs tcpserver under the qmaild uid ## -g 81 runs tcpserver under the qmaild gid ## 0 indicates tcpserver is running on this machine ## smtp (...)qmail-smtpd specifies to pass SMTP connections to qmail-smtpd ## ... or ... ## 2525 (...)qmail-smtpd specifies to pass connections on port 2525 to qmail-smtpd ## rblsmtpd checks for blacklisted IP addresses before accepting SMTP ## -b specifies an SMTP 553 error code to return to blacklisted servers ## -r is specified before each successive RBL source ## descriptor 2 is sent to splogger to create standard log entries attributed to rblsmtpd ## end the line with & or the process hangs the console that starts it! ## echo "tcpserver-SMTP started" ;; stop) ## no action needs to be taken to kill tcpserver processes ## exit 0 ;; *) echo "Usage: leave this script alone, it's for boot only." exit 64 ;; esac
So why are we running another instance of tcpserver on port 2525, as well as the standard one on port 25? Because there are a lot of ISPs these days that are blocking all traffic to destination port 25 anywhere outside their own network. So you will probably want to be able to set up your mail clients, on portable machines, to access your authenticated SMTP on a non-standard port to get around that limitation. I use 2525 because it's easy to remember, but of course you can pick whatever you like.
Whew! Now let's make sure our tcpserver.sh script is executable, then fire it up and make sure tcpserver is running.
ph34r# chmod 755 /usr/local/etc/rc.d/tcpserver.sh ph34r# /usr/local/etc/rc.d/tcpserver.sh start tcpserver-SMTP started. ph34r# ps ax | grep tcpserver 87717 p0 S 0:00.00 /usr/local/bin/tcpserver -H -l0 -R -c 512 -x /etc/tcp 87719 p0 S 0:00.00 /usr/local/bin/tcpserver -H -l0 -R -c 512 -x /etc/tcp
Great - now that we've fired up Dovecot and tcpserver both, and confirmed that they're running, let's make sure they're also working the way they're supposed to.
Testing SMTP, IMAP, and POP3 via Telnet
As our first step in testing the server's basic functions, we'll want to test the tcpserver / Qmail combo by simulating some incoming traffic - which will also then give us an email to check for the presence of in our IMAP and POP3 tests later.
ph34r# telnet localhost 25 Trying 127.0.0.1... Connected to localhost.localdomain. Escape character is '^]'. 220 ESMTP HELO justtesting 250 MAIL FROM: email@example.com 250 ok RCPT TO: firstname.lastname@example.org 250 ok DATA 354 go ahead Subject: this is a test message Just testing SMTP functionality by telnetting in to port 25. I'll end this message now by entering in a line with nothing but a period in it and hitting return. . 250 ok 1103093638 qp 87827 QUIT 221 Connection closed by foreign host.
Okay - our server just accepted a telnet connection, responded like a mailserver, and accepted a nice little test email to the postmaster account at the domain we set up earlier. Now let's make sure that we can see that email using the IMAP protocol:
ph34r# telnet localhost 143 Trying 127.0.0.1... Connected to localhost.localdomain. Escape character is '^]'. * OK dovecot ready. A LOGIN email@example.com thisismypassword A OK logged in. A SELECT inbox * FLAGS (\Answered \Flagged \Deleted \Seen \Draft) * OK [PERMANENTFLAGS (\Answered \Flagged \Deleted \Seen \Draft \*)] Flags permitted. * 1 EXISTS * 1 RECENT * OK [UIDVALIDITY 1103088195] UIDs valid * OK [UIDNEXT 1] Predicted next UID A OK [READ-WRITE] Select completed. A LOGOUT * BYE Logging out A OK Logout completed. Connection closed by foreign host.
Great! By using telnet, we've just verified on a very direct level that our IMAP server answers incoming connections, successfully authenticates users, and successfully opens their inboxes - see the * 1 EXISTS and * 1 RECENT lines? That's the email we telnetted in earlier. So, if we have any problems trying to set up IMAP accounts on actual clients later, now we know that they're client problems or network problems - not server configuration problems. Verifying these things ahead of time will make your life MUCH easier.
Now let's test POP3 (assuming you want to allow clients to use POP3 as well):
ph34r# telnet localhost 110 Trying 127.0.0.1... Connected to localhost.localdomain. Escape character is '^]'. +OK dovecot ready. USER firstname.lastname@example.org +OK PASS thisismypassword +OK Logged in. LIST +OK 1 messages: 1 354 . QUIT +OK Logging out. Connection closed by foreign host.
Tested, confirmed, and good to go!
Configuring Email Clients
Well, we're all done now - we've got a fully functioning mailserver that can handle sending and receiving mail, authenticated SMTP (with and without TLS encryption), webmail, virtual domains, delegation of administration by domain and by individual mailbox, IMAP storage, POP3 for people who can't use IMAP, spam filtering by RBL, and more. Once you've set up your domains and your user accounts (and don't forget for every domain you set up, you will also need DNS pointing the mail services for that domain to this server, which isn't covered in this article), the only thing left is configuring your clients. Here's a few basic bullets to help you with common SNAFUs with that:
- remember to set the "username" as email@example.com, not just "mailbox"
- remember that in order to send email, the client either has to be on the network named in /etc/tcp.smtp (actually in the compiled version, /etc/tcp.smtp.cdb) or has to login using Authenticated SMTP
- remember that if you expect the client machine to be able to connect reliably from foreign networks, you should configure it to connect to your SMTP server on a nonstandard port
- remember that if you're using a self-signed certificate, you will get security warnings from some clients if you use TLS encryption, and some other clients (notably Microsoft Outlook) will refuse to connect at all using TLS encryption if your certificate is self-signed
And that's pretty much it - enjoy!