Knowledge Base

Unable to send email in Plesk: mail transport unavailable

Symptoms

There are lots of undelivered outgoing emails on the Plesk server. It is not possible to send mail and messages get stuck in the mail queue.
The following errors are logged in /var/log/maillog:

postfix/smtp[715642]: connect to example.com[203.0.113.2]:587: Invalid argument
postfix/smtp[715642]: 8A0FA1D2090C: [email protected], relay=none, delay=470, delays=470/0.01/0.16/0, dsn=4.4.1, status=deferred (connect to example.com[203.0.113.2]:587:
Invalid argument)

postfix/qmgr[14111]: warning: connect to transport private/203.0.113.2-: Connection refused
postfix/error[21724]: 0A1322CF16C: [email protected], relay=none, delay=0.07, delays=0.03/0.01/0/0.02, dsn=4.3.0, status=deferred (mail transport unavailable)

Cause

Postfix is misconfigured.

Resolution

Connect to the server via SSH.

If there are no custom settings in Postfix's configuration, execute plesk repair mail utility:

# plesk repair mail -y

If there are some custom settings and the issue should be resolved more accurately, verify the following:

Transport settings are set as below:

# postconf -n | grep -i transport
sender_dependent_default_transport_maps = hash:/var/spool/postfix/plesk/sdd_transport_maps
transport_maps = , hash:/var/spool/postfix/plesk/transport
virtual_transport = plesk_virtual
Transport may be defined in sender_dependent_default_transport_map if Send from domain IP addresses option is set in Tools & Settings > Mail Server Settings:

# postmap -s /var/spool/postfix/plesk/sdd_transport_maps
@example.com plesk-203.0.113.2-:
@example2.com plesk-203.0.113.3-:

Note: 203.0.113.x should be replaced with the server's IP addresses.
If so, the entries from sdd_transport_maps are defined in the first column of smtp_bind_address option. smtp_bind_address is an optional numerical network address that the Postfix SMTP client should bind to when making an IPv4 connection.

# grep "smtp_bind_address" /etc/postfix/master.cf
plesk-203.0.113.2- unix - n n - - smtp -o smtp_bind_address=203.0.113.2 -o smtp_bind_address6= -o smtp_address_preference=ipv4
plesk-203.0.113.3- unix - n n - - smtp -o smtp_bind_address=203.0.113.3 -o smtp_bind_address6= -o smtp_address_preference=ipv4
To be able to connect, smtp_bind_address needs to be defined as mentioned in the mynetworks section and the binding name should be the same as defined in sdd_transport_maps:

# postconf mynetworks
mynetworks = 127.0.0.0/8 [::1]/128 203.0.113.2/32, 203.0.113.3/32

Starting from Plesk 12, it should be empty:

# postconf mynetworks
mynetworks =

unless there are white-listed IP addresses in Plesk > Tools & Settings > Mail Server Settings > White List tab. If so, they will be added to mynetworks section.
Restart the service:

# service postfix restart