For the record, ever since the last patches for NFS got committed, we don't see locking issues over NFS in general across all our platforms, but it also depends on how you configure your NFS server.

You might find that this is not a dovecot issue, but an NFS issue.

You might want to post more about your NFS setup(s) and then someone on the list might better assist you.

Thank you, Michael, for the advice.  Turns out the NFS locking problem was a firewall issue on the Dovecot server, which is now fixed.

Does anyone have any advice on the the Submission Service authentication?

For example, this is what's coming up in the logs:

Sep 25 14:39:04 triata4 dovecot: submission-login: Client has quit the connection (auth failed, 1 attempts in 2 secs): user=<%u>, method=PLAIN, rip=10.1.1.99, lip=10.1.1.99, TLS, session=<mrNJe2eTDMUKAQFj>

As you can see, it's choking on user=<%u>, which it's not expanding, so is there a variable I can put in there, or is it strictly hard coded authentication?

Thanks.