E-Mail server hosting

Everything in the following page is directly taken (and adjusted to my liking) from The Gentoo Virtual Mail Server guide which is a deep and very detailed read on the topic. I will stray a little bit from that guide.

I will show you how to install and interconnect:

• Postfix, the MTA (Mail Transfer Agent)
• Dovecot, the IMAP server
• NGINX + PHP-FPM for web access (admin console + webmail)
• PostfixAdmin, the email configuration WEB gui
• Roundcube
• OpenDKIM
• OpenDMARC
• Spamassassin

Install Postfix and Dovecot

USE flags:

echo "*/* maildir dovecot sasl" >> /etc/portage/package.use/mailserver
echo "net-mail/dovecot managesieve sqlite lz4" >> /etc/portage/package.use/mailserver
echo "mail-mta/postfix dovecot-sasl sqlite -sasl" >> /etc/portage/package.use/mailserver 

Emerge the servers:

emerge -vp postfix dovecot

Since different pieces of the email infrastructure will need to interoperate, it is a good idea to create a specific user to store all the emails on the filesystem. This user will own the email storage folders which i assume will be located under /home/vmail. I choose UID and GID 5000 since the ones <1000 are reserved for system users:

groupadd -g 5000 vmail
useradd -m -d /home/vmail -s /bin/false -u 5000 -g vmail vmail
chmod 2770 /home/vmail/

The resulting permissions should look like:

ls -ld /home/vmail
drwxrws--- 3 vmail vmail 4096 Aug 2 07:24 /home/vmail

postfixadmin and roundcube will be installed manually and not via Gentoo portage, to avoid upgrade issues.

FILE /etc/postfix/main.cfBinding UID and GID's to postfix

# Link the mailbox uid and gid to postfix.
virtual_uid_maps = static:5000
virtual_gid_maps = static:5000
 
# Set the base address for all virtual mailboxes
virtual_mailbox_base = /var/vmail