Mail: Difference between revisions

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* POP3
* POP3
** No longer supported.
** Hostname:
** Port: 110 (POP3), 995 (POP3S)
** POP3 is considered deprecated. We would like to get rid of it someday, so please don't use it unless no other alternatives exist for you.


Revision as of 20:30, 22 May 2012

Mail services are currently handled by caffeine.

Reading your mail

You can use any user agent that supports maildir locally (mutt, alpine, etc), and any client that supports POP3 or IMAP either locally or remotely. We also have webmail.

Here are the details:

  • maildir
    • Location: $HOME/.maildir/
  • POP3
    • No longer supported.
  • IMAP
    • Hostname:
    • Port: 143 (IMAP), 993 (IMAPS)
  • SMTP
    • Hostname:
    • SSL encryption and authentication required
    • Port: 25, 465, or 587


By default, we do not run any Bayesian Spamfilters on user email, as they stand a chance of false-positives leading to users not recieving legitimate mails. However, you can configure procmail (the application that postfix calls to deliver any mail that it recieved to the user that it was sent to) to pipe your message through spamassassin, and then optionally place it in special folders and/or delete it based on its spam score and/or whether it got flagged as spam or not. In order to do this, you need to configure procmail via .procmailrc in your home directory. An example such .procmailrc is below:

#Begin spamfilter-enabled procmailrc

 #Spamassassin start
 :0fw: spamassassin.lock
 | /usr/bin/spamc
 #Spamassassin end

 * ^X-Spam-Status: Yes
 #End spamfilter-enabled procmailrc

Technical Details

Mail Transfer (Incoming)

Postfix is our MTA and runs on mail. Incoming mail is received inbound on smtp/25 or ssmtp/465 and goes through a sequence of filters before being delivered to users.

We are using the following filters for incoming mail, to combat spam and malware:

  • RBL
  • Greylisting with postgrey

These filters reject truckloads of spam, preventing them from reaching your inbox. Greylisting adds a delay to mail delivery from unknown servers, but after a small number of successes they will be auto-whitelisted. If that isn't good enough, ask to whitelist all mail to your address.

Mail Delivery

User mail is delivered, by default, to procmail. This is configurable by adding a comma-separated list of destinations in $HOME/.forward. See aliases(5) for more details.

Procmail, in turn, writes mail to $HOME/.maildir unless instructed otherwise. You can customize procmail by editing $HOME/.procmailrc. See procmailrc(5) for more details.


If you are out of quota or another error occurs writing to your home directory, procmail will deliver your message to /var/mail/$USER on the mail server. If that too fails, caffeine is probably on fire. The message will be returned to the queue where it will eventually bounce.

Mail Retrieval

We run Dovecot, a POP3 and IMAP server. It reads messages from $HOME/.maildir, so if you have procmail deliver your mail elsewhere you will be unable to retrieve your mail using POP3 or IMAP.

Mail Submission (Outgoing)

On caffeine, outgoing mail is submitted directly to Postfix via the sendmail(1) wrapper or on submission/587. Submitted mail is then queued for delivery to its destination. The other systems have no MTA and instead run sSMTP, which relays mail through caffeine immediately without any queue or daemon.