Emails are not sending; (99) Cannot assign requested address.

Symptoms

The Exim mail queue is building and mail is not leaving the server.

Description 

When checking the Exim Mainlog, Where are the Exim logs?, I see "Cannot assign requested address". How can I resolve this?

Workaround

The issue comes from the IP not being bound to the server. Make sure that the IP is listed in /etc/mailips and if it is not, add the IP to the mailips file. The format of /etc/mailips is:

example.com: 192.0.2.0
sub.example.com: 192.0.2.1
example.net: 192.0.2.2
addon.example.net: 192.0.2.3
*: 192.0.2.4

If this file already contains an entry, verify the IP is bound to the system with ifconfig and if the IP is not present through ifconfig, you will want to verify the IP address is present in /etc/ips. If it is, you can run /scripts/restartsrv_ipaliases to restart the ipaliases service to bind the IP to the network interface. 

If your server is using NAT you may also need to run /scripts/build_cpnat and then restart Ipaliases:

/scripts/restartsrv_ipaliases

Finally, start a queue run.

exim -qf &