[exim] Outlook and "too many messages in one connection"

I have a series of odd entries in my log which I cannot explain. I am using
Exim-4.50 and the user submitting messages used Microsoft Office Outlook, Build
11.0.5510.

He appears to have had several messages queued in his Outlook Outbox when he
started the program (while connected via our dial-up service).

The logs shows his PC sending one message (two recipients) which was processed
without a problem. Immediately after the log entry for that submission, with
the same timestamp, there is an entry with his PC's IP address saying "too many
messages in one connection". 38 seconds later there is another, 10 seconds
after that there is another and so on with a total of 8 such lines.

He claims to have received no error report from Outlook and his Outbox is
empty. His Sent Items folder shows 8 sent messages which do not appear in the
Exim log.

I can find no evidence in the Exim log for all the messages which would be
needed to get to the "too many messages in one connection" state (controlled by
the smtp_accept_max_per_connection option).

Any suggestions as to what Outlook could have been doing?

Phil.
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Phil Chambers (postmaster@???)
University of Exeter