imapc_port not working

Hi, Dovecot v2.3.7.2 on Ubuntu 18.04LTS

I have configured for imap proxy to imap.gmail.com However whilst the imapc_host setting is working, imapc_port is not - it ignores the value I set and dovecot always tries to connect to gmail on port 143 (as per error log output). I have the imapc settings in the 10-mail.conf which gets loaded by dovecoat.conf Looks like a bug. Any assistance would appreciated. Regards,David.