Issue with LMTP proxying and port number

[Steven Craig]

Hello there,

Everything was working fine on Dovecot 2.2.10 (on CentOS 7), but after 
updating to version 2.2.36, our director servers are not able to proxy LMTP.

We are sending mail from exim to the local Dovecot LMTP socket, which 
then used to send it to our internal mail servers on port 24.

Besides the update, nothing has changed in the config files.  The 
configuration has been working great for months … Then we had a great 
idea of doing holiday maintenance.

(Currently, we are working around this issue by having exim send mail to 
the IP and port, instead of the socket.)

Doing a tcpdump capture shows no TCP traffic either.  The logs seem to 
say that it is trying to go to port 0, so my guess is that it’s not 
getting the port directive from either static or sql — since the docs 
state that if these settings aren't specified, it will always use the 
same connection type for the proxy that it received the connection on.

Any thoughts?  I can share config if necessary.