[Exim] Do Return Receipts Have to be Null Senders?

I happen to be working on a mail problem with an IBM tech and noticed that
all of his return Receipt messages arrive as regular mail instead of as a
Null Sender.

I thought this was improper?

Perhaps they are doing this because sites are blocking Null Senders??

I can see a mail loop as a result of this under the right conditions.

Curious if this is considered acceptable. All of our return receipts go
out as Null Sender mail.

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Kevin W. Reed - TNET Services, Inc.
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