IPv4/IPv6 mismatches of doveadm: Fatal: connect(fd00:b::1:12345) failed: Connection refused

Hi —

I recently extendend my IPsec tunnel between two mail servers to deal with IPv4 addresses in addition to IPv6 ones. (No specific reason for that.) I ran into an issue worth reporting. This is Dovecot v2.2.27 (c0f36b0) at FreeBSD STABLE-11.

Previously:

dovecot.conf:
	plugin { 
		mail_replica = tcp:remote.test
	}
	service doveadm {
	inet_listener {
		address = [::]
		}
	}	

| local> host remote.test:	
remote.test has IPv6 address fd00:b::1

working well.

Currently:

dovecot.conf:
	plugin { 
		mail_replica = tcp:remote.test
	}
	service doveadm {
	inet_listener {
		address = *
		}
	}	

| local> host remote.test:	
remote.test has address 10.2.0.1
remote.test has IPv6 address fd00:b::1

Now, Replication stops and throws an error like:

| <mail.crit> local.test dovecot: doveadm(user): Fatal: connect(fd00:b::1:12345) failed: Connection refused

If I either

#) remove IPv6 from my lokal DNS, 
#) use "mail_replica = tcp:10.2.0.1", or 
#) define the appropriate IPv4 address of remote.test in /etc/hosts, 

then replication works as usual.

Hmm, shouldn't doveadm be more persistent in using every IP address of that entry of mail_replica *before* throwing a "Fatal:" error? Or do I miss something, and it's a feature, instead?

Regards, Michael