Notes on mail server configuration.

mail-server-notes.md

WORK IN PROGRESS

Mail Server Configuration with Virtual Domains

Security Basics

• Use SSL. You're passing credentials and private communications over the wire, so you'd better encrypt it.
• Don't be an open relay. Forwarding spammers' mail is a good way to get your IP blacklisted and receive some nastygrams from other webmasters
• chroot if possible.

Software

I use Postfix and Dovecot. They're reasonably well-behaved.

sudo apt-get install postfix dovecot-imapd

That will get you the base packages necessary to get started.

Basic Postfix

Postfix is a popular and sensibly-written mail transfer agent (MTA). It's full-featured and fast.

Main Configuration: /etc/postfix/main.cf

main.cf is Postfix's primary configuration file.

Basic Variables

• myhostname: this mail server's hostname
• myorigin: domain to use for locally-posted mail sending and delivery
• mydestination: domains whose mail is handled by this server
• mynetworks: trusted networks (i.e., the IP block(s) your other non-mail servers are in)
• relayhost: domain to relay mail to when the destination is not a domain in mydestination
• inet_interfaces: the interfaces Postfix should listen on. Normally, all
• home_mailbox: the pathname to deliver mail to relative to a user's home directory
• alias_maps/alias_database: aliases used for local mail delivery

Virtual Domain Variables

• ``

A Basic main.cf

# Use /etc/mailname to determine origin
myorigin = /etc/mailname
myhostname = mail.domain.net
# Accept mail for localhost and domain.net
mydestination = domain.net, mail.domain.net, localhost, localhost.localdomain
# Allow loopback deliveries and deliveries from a hypothetical server block
# at 192.168.1.0/24
mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128 192.168.1.0/24
# Don't relay mail not destined for here
relayhost = 
# Listen on all interfaces
inet_interfaces = all

# Use qmail Maildir format
# -- qmail format used if name has a trailing /
home_mailbox = Maildir/

# Configure alias files
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases

# Allow user+tag@domain.net style addressing
recipient_delimiter = +

# Set a connection banner
smtpd_banner = $myhostname ESMTP $mail_name

# Disable local mail notifications
biff = no

# Unlimited mailbox size
mailbox_size_limit = 0

Basic Dovecot

Dovecot is one of the popular IMAP client access servers. Like Postfix, it has a rich feature set and solid performance.

Virtual Mail

If you're just doing email for a single domain, and you (or people you trust with local accounts) are the only user, you can just create the requisite system accounts and aliases and call it a day. Otherwise, you'll need to roll some of the virtual mail features of Postfix and Dovecot.