[Dovecot] retr errors

[Bill Morgan]

My ISP uses Dovecot and I have had an ongoing problem
for a while using several email clients.

Sometimes the response to a retr request is mal-formed. The expected 
response
"+OK nnn octets" is not returned. The response looks like it
started somewhere in the message headers.

Sometimes a retry can clear the
problem but I usually need to delete the first message via a putty session.

The problem, when present, is always on the first message. Never seen
it in the middle of a series of messages. This problem has been seen on
different machines, different versions of Windows, at home and on the road.

I have wireshark traces showing good and bad sessions....
======================
stat
+OK 93 1000437
retr 1
+OK 6946 octets
Return-path: .....
=========================
retr 1
  of blahblah at blah.com designates 2607:f8b0:4001:c03::235
  as permitted sender) smtp.mail=blahblah at blah.com;       dkim=pass 
header.i=@blah.com
Reply-To: android-developers at googlegroups.com
Precedence: list
Mailing-list: ......
==================
My ISP has been non-helpful. Any ideas how I can track
down the problem?

Thanks
Bill