17 May 2019: Copying emails to external accounts added.
7 May 2019: "gksudo gedit" changed to "sudo gedit" as Ubuntu 18.04 dropped "gksudo". Header_checks added. Auto creation of Trash folders added. Webmaster added.
29 Sep 2018: Add "body_checks" for spam control.
20 Sep 2018: Increase message_size_limit to 20 times the default.
5 Apr 2018: Increase message_size_limit to 10 times the default.
25 Dec 2018: Published on web.
12 Apr 2014: Specify maximal_queue_lifetime to notify unsuccessful delivery immediately.
2 Apr 2014: Specify fully qualified domain name.
Note
Postfix is a mail transfer agent (MTA) responsible for sending out and receiving emails between servers.
Dovecot is a mail delivery agent (MDA) responsible for sending out and receiving emails between a server and its users.
Mail-stack-delivery is a combined package containing both Postfix and Dovecot. It would be easier than to install Postfix and Dovecot separately.
Re-direct to server ports
Set the internet router to re-direct the following connections to server ports:
- SMTP = port 25 (for receiving or sending emails)
- secure SMTP = port 465 (for receiving or sending emails securely)
- IMAP = port 143 (for retrieving emails)
- secure IMAP = port 993 (for retrieving emails securely)
- POP3 = port 110 (for retrieving emails)
Install both Postfix and Dovecot
Install the combined package:
$ sudo apt-get install mail-stack-delivery
Reconfigure Postfix
Reconfig:
$ sudo dpkg-reconfigure postfix
Use Tab key to change selection.
Select "Internet Site".
Enter the following information:
System mail name: <fully qualified domain name, such as "kctang.com.hk"> Root and postmaster mail recipient: <such as "kctang"> Other destinations to accept mail: <fully qualified domain name, such as "kctang.com.hk">, <server name such as "server1">, localhost.localdomain, localhost Force synchronous updates on mail queue: No Local networks: 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128 Use procmail for local delivery: No Mailbox size limit (bytes): 0 Local address extension character: + Internet protocols to use: all
Activate the changes:
$ sudo systemctl reload postfix or $ sudo service postfix reload
Edit "main.cf" settings:
$ sudo gedit /etc/postfix/main.cf
Specify:
myhostname = kctang.com.hk # last line changed from server name to fully qualified domain name, # otherwise some servers would not accept e-mails sent without fully qualified domain name, 2/4/2014 message_size_limit = 204800000 # last line added to increase the default 10 times, 5/4/2014 # increased to 20 times, 20/9/2018 maximal_queue_lifetime = 0 # last line added to report unsuccessful delivery immediately instead of after the default of 5 days, 12/4/2018 body_checks = regexp: /etc/postfix/body_checks # last line added to refer to another file to check contents of email bodies, 29/9/2018 header_checks = regexp:/etc/postfix/header_checks # last line added to check headers, KCTang 30/9/2018
Edit "master.cf" settings:
$ sudo gedit /etc/postfix/master.cf
Specify:
smtp inet n - y - - smtpd smtps inet n - y - - smtpd # last line uncommented -o smtpd_sasl_auth_enable=yes # last line added to enable STARTTLS authentication -o smtpd_client_restrictions=permit_sasl_authenticated,reject # last line added to reject if not authenticated, no space after "," -o smtpd_tls_wrappermode=yes # last line added to force use of TLS -o milter_macro_daemon_name=ORIGINATING # last line added
Create "body_checks" file:
$ sudo gedit /etc/postfix/body_checks
Specify one or more lines of texts within //:
/unique text contained in email you do not want to receive/ DISCARD
"DISCARD" means delete from the server.
Create "header_checks" file:
$ sudo gedit /etc/postfix/header_checks
Specify similarly.
(header_checks added 7 May 2019)
Change Dovecot settings
Edit config file:
$ sudo gedit /etc/dovecot/conf.d/99-mail-stack-delivery.conf
Specify:
mail_location = maildir:~/Maildir:LAYOUT=fs
# LAYOUT=fs added to last line, to use "/" instead of "." to denote sub-folders
# IMAP configuration
protocol imap {
mail_max_userip_connections = 1000
# 10 in last line increased to 1000
imap_client_workarounds = delay-newmail
}
# POP3 configuration
protocol pop3 {
mail_max_userip_connections = 50
# 10 in last line increased to 50
pop3_client_workarounds = outlook-no-nuls oe-ns-eoh
}
# The following are additional to those in 15-mailboxes.conf.
# They are to auto create Trash folders.
# Trash folders would not be backed up with back-in-time,
# and therefore would need to be re-created after email recovery is done from back-in-time.
namespace inbox {
mailbox Trash {
auto = subscribe
}
}
(trash folder setting added 7 May 2019)
Activate the changes:
$ sudo systmctl reload postfix or $ sudo service postfix reload and $ sudo systemctl restart dovecot or $ sudo service dovecot reload
Verify success
See whether the Postfix server is running:
$ telnet localhost 25
should display:
220 kctang.com.hk ESMTP Postfix (Ubuntu)
ehlo localhost
should display the following:
250-kctang.com.hk
250-PIPELINING
250-SIZE 102400000
250-VRFY
250-ETRN
250-STARTTLS
250-ENHANCEDSTATUSCODES
250-8BITMIME
250 DSN
Ctrl-]
to exit to "telnet >" prompt.
quit
to exit telnet.
Try also:
$ telnet localhost 995
similarly:
$ telnet localhost 465
should display either one:
Connected to localhost
Connected to kctang.com.hk
"Ctrl-]"
to exit to "telnet >" prompt.
quit
to exit telnet.
Specify internal email forwarding
Edit "aliases" file:
$ sudo gedit /etc/aliases
Specify:
postmaster: kctang webmaster: kctang kctcl: kctcl, kctclpop
meaning:
- forwarding e-mails sent to postmaster@localhost and webmaster@localhost to kctang@localhost, no email will be left at postmaster or webmaster
(webmaster added 7 May 2019)
- forwarding e-mails sent to kctcl@localhost to kctcl@localhost (itself) and to kctclpop@localhst, i.e. making a copy
"localhost" means "kctang.com.hk" in our case. For the email user name before "@", there is no need to create a file system user account for it if all emails addressed to it are forwarded elsewhere. The name serves as an alias only of the email account forwarded to.
(added 17 May 2019)
Activate setting everytime the "aliases" file has been changed:
$ sudo newaliases
Copy to external email accounts
(section added, 17 May 2019)
Execute:
$ sudo gedit /etc/postfix/main.cf
Specify at the end of the file:
virtual_alias_domains = kctang.com.hk virtual_alias_maps = hash:/etc/postfix/virtual
Execute:
$ sudo gedit /etc/postfix/virtual
Specify to make a copy to itself and a copy to the external email account:
# from to one or more addresses, separated by a space kctang@kctang.com.hk kctang@kctang.com.hk name1@external.account.name kctcl@kctang.com.hk kctcl@kctang.com.hk name2@external.account.name
Omit making a copy to itself if only email forwarding is required.
Save and exit.
Execute the first time the "virtual" file is created:
$ sudo postmap /etc/postfix/virtual
Execute:
$ sudo systemctl restart postfix
Test by sending emails.