[exim] no valid sender in any header line

I have an odd situation that I have not noticed before.

In my RCPT ACL I do 'verify = sender/callout' and record the result for spam-scoring later.

In my DATA ACL I do 'verify = header_sender' (note: with no callout).

I have messages with both an envelope sender and a header From: of westlaw@???.

If you do a callout for westlaw@??? you get a failure.

The 'verify = header_sender' should not fail because westlaw.co.uk is a registered domain and has MX records. However, it is failing and so the messages are being rejected with 'no valid sender in any header line'.

I can only assume that the result of the 'verify = sender/callout' is being cached and used to cause the 'verify = header_sender' to fail as well.

Can anyone confirm that this is indeed the case. If it is then surely it is a bug because the options are different in the two cases.

If the header_sender is not failing because of a cached result then I am mystified as to why it is failing!

Thanks for any comments,

Phil.
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Phil Chambers
Postmaster
University of Exeter