Jack Moore

Email: jack(at)jmoore53.com
Project Updates

Semi Custom Mail Server

Written by: Jack
27 Jul 2020 » system administration, config, Poxtfix, Dovcot, Mailgun, Mailspring, Custom Email Server

I’ve always wanted a custom mail server. This attempts to cover my endeavors in the topic and serves as a howto guide for setting up a Postfix/Dovecot/Mailgun Server on a DigitalOcean server.

Please note most VPS providers block outbound on port 25, but allow inbound which will allow us to use postfix/dovecot for inbound messages, and I am using postfix/mailgun for outbound emails.

Dovecot Config for the Beginner

Step 1: Make sure to cop that SSL Cert from Letsencrypt!

Install Dovecot.. Make Dovecot Config look like this:

(But first understand this config file is not an end all be all to config files for dovecot. I am 99.99% sure this file will change due to the fact I want a mysql backend setup for virtual domains. This means, yes, I will be setting up a front end for people to buy and host email services. I just need to figure out SMTP authentication with Mailgun first. Their reset password method is quite a beast and I will likely need a wrapper class for it…)

disable_plaintext_auth = no
mail_privileged_group = mail
mail_location = mbox:~/mail:INBOX=/var/mail/%u
userdb {
  driver = passwd
}
passdb {
  args = %s
  driver = pam
}
protocols = " imap"

protocol imap {
  mail_plugins = " autocreate"
}
namespace inbox {
  # prefix = INBOX. # the namespace prefix isn't added again to the mailbox names.
  inbox = yes
  # ...

  mailbox Trash {
    auto = no
    special_use = \Trash
  }
  mailbox Drafts {
    auto = no
    special_use = \Drafts
  }
  mailbox Sent {
    auto = subscribe # autocreate and autosubscribe the Sent mailbox
    special_use = \Sent
  }
  mailbox "Sent Messages" {
    auto = no
    special_use = \Sent
  }
  mailbox Spam {
    auto = create # autocreate Spam, but don't autosubscribe
    special_use = \Junk
  }
  mailbox virtual/All { # if you have a virtual "All messages" mailbox
    auto = no
    special_use = \All
  }
}

service auth {
  unix_listener /var/spool/postfix/private/auth {
    group = postfix
    mode = 0660
    user = postfix
  }
}

ssl=required
ssl_cert = </etc/letsencrypt/live/mail.jmoore53.com/fullchain.pem
ssl_key = </etc/letsencrypt/live/mail.jmoore53.com/privkey.pem

Gotchas

Error Mailbox Sent: Failed to Autocreate Mailbox: Permission Denied

Logs:

Jul 27 19:18:17 mail dovecot: master: Dovecot v2.3.7.2 (3c910f64b) starting up for imap (core dumps disabled) Jul 27 19:18:19 mail dovecot: imap-login: Login: user=, method=PLAIN, rip=1.1.1.1, lip=1.1.1.1, mpid=26650, TLS, session=<8ap1L3GrPpZKU9sj> Jul 27 19:18:19 mail dovecot: imap(jack)<26650><8ap1L3GrPpZKU9sj>: Warning: autocreate plugin is deprecated, use mailbox { auto } setting instead Jul 27 19:18:22 mail dovecot: imap-login: Login: user=, method=PLAIN, rip=1.1.1.1, lip=1.1.1.1, mpid=26652, TLS, session= Jul 27 19:18:22 mail dovecot: imap(jack)<26652>: Warning: autocreate plugin is deprecated, use mailbox { auto } setting instead Jul 27 19:18:22 mail dovecot: imap(jack)<26652>: Error: Mailbox Sent: Failed to autocreate mailbox: Permission denied Jul 27 19:18:22 mail dovecot: imap(jack)<26652>: Error: Mailbox Spam: Failed to autocreate mailbox: Permission denied

Fix (Give correct ownership and permissions to user):

sudo useradd jack
sudo mkdir /home/jack/mail
sudo chown jack:jack /home/jack/mail
sudo chmod -R 700 /home/jack/mail

Dovecot < Character in SSL Configuration

SSL was unable to create a connection. Was giving the error no CA was signing the certificate however the certificate was already generated.

Running below would barf out an error and prevent any kind of login:

openssl s_client -connect mail.jmoore53.com:993 -quiet

Fix:

ssl=required
ssl_cert = </etc/letsencrypt/live/mail.jmoore53.com/fullchain.pem
ssl_key = </etc/letsencrypt/live/mail.jmoore53.com/privkey.pem

Configuring SMTP

Errors showing something along the lines of (below) for a user’s mailbox:

Jul 27 15:44:41 mail dovecot: imap(jack)<24052>: Error: Mailbox Spam: Failed to autocreate mailbox: Internal error occurred. Refer to server log for more information. [2020-07-27 15:44:41] Jul 27 15:46:23 mail dovecot: imap(jack)<24052>: Error: file_dotlock_open(/home/jack/mail/.imap/dovecot.list.index.log) failed: Permission denied (euid=1000(jack) egid=1000(jack) missing +w perm: /home/jack/mail/.imap, dir owned by 0:0 mode=0755) Jul 27 15:46:23 mail dovecot: imap(jack)<24052>: Error: Couldn't create mailbox list lock /home/jack/mail/.imap/mailboxes.lock: file_create_locked(/home/jack/mail/.imap/mailboxes.lock) failed: safe_mkstemp(/home/jack/mail/.imap/mailboxes.lock) failed: Permission denied Jul 27 15:46:23 mail dovecot: imap(jack)<24052>: Error: Mailbox Sent: Failed to autocreate mailbox: Internal error occurred. Refer to server log for more information. [2020-07-27 15:46:23] Jul 27 15:46:23 mail dovecot: imap(jack)<24052>: Error: Couldn't create mailbox list lock /home/jack/mail/.imap/mailboxes.lock: file_create_locked(/home/jack/mail/.imap/mailboxes.lock) failed: safe_mkstemp(/home/jack/mail/.imap/mailboxes.lock) failed: Permission denied Jul 27 15:46:23 mail dovecot: imap(jack)<24052>: Error: Mailbox Drafts: Failed to autocreate mailbox: Internal error occurred. Refer to server log for more information. [2020-07-27 15:46:23] Jul 27 15:46:23 mail dovecot: imap(jack)<24052>: Error: Couldn't create mailbox list lock /home/jack/mail/.imap/mailboxes.lock: file_create_locked(/home/jack/mail/.imap/mailboxes.lock) failed: safe_mkstemp(/home/jack/mail/.imap/mailboxes.lock) failed: Permission denied Jul 27 15:46:23 mail dovecot: imap(jack)<24052>: Error: Mailbox Archive: Failed to autocreate mailbox: Internal error occurred. Refer to server log for more information. [2020-07-27 15:46:23] Jul 27 15:46:23 mail dovecot: imap(jack)<24052>: Error: Couldn't create mailbox list lock /home/jack/mail/.imap/mailboxes.lock: file_create_locked(/home/jack/mail/.imap/mailboxes.lock) failed: safe_mkstemp(/home/jack/mail/.imap/mailboxes.lock) failed: Permission denied Jul 27 15:46:23 mail dovecot: imap(jack)<24052>: Error: Mailbox Trash: Failed to autocreate mailbox: Internal error occurred. Refer to server log for more information. [2020-07-27 15:46:23] Jul 27 15:46:23 mail dovecot: imap(jack)<24052>: Error: Couldn't create mailbox list lock /home/jack/mail/.imap/mailboxes.lock: file_create_locked(/home/jack/mail/.imap/mailboxes.lock) failed: safe_mkstemp(/home/jack/mail/.imap/mailboxes.lock) failed: Permission denied Jul 27 15:46:23 mail dovecot:

Fix:

mkdir -p /home/jack/mail/.imap
chown jack:jack /home/jack/mail/.imap/

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