This issue is now nearly three years old.

@Tom: if you read this now and if this topic is still important
for you, please reply.

Summary: The behaviour of Roundup setting Reply-To: to the tracker
instance is important to keep email discussions archived in issues.
Citing from doc/overview.txt:

 Submission and Discussion
 -------------------------
 ...
 2. All e-mail messages sent by Roundup have their "Reply-To:"
    field set to Roundup's address, and have the item's
    number in the "Subject:" field.  Thus, any replies to the
    initial announcement and subsequent threads are all received
    by Roundup.  Roundup notes the item number in the "Subject:"
    field of each incoming message and appends the message
    to the appropriate spool.

But sometimes this behaviour might not be desirable.  See msg4832,
msg4834 for an use case explanation.
I've modified the title of this issue to make this request clearer.

Adding a new configuration option handling the Reply-To:-header 
as suggested by Bernard in msg4835 now does not look very hard
for me (including tests and doc I estimate I would only a hour or so).
But personally I've no strong need for this feature.

Best regards, Peter.