when From: != Reply-To:

Henry Smith Jr. asked,

| I could be wrong on this example also, but excluding list(s), is
| there a valid reason for the Reply-To: and From: not to match on person to
| person mail?

Yes, very often ... if someone asks you to help out somebody else, or if the
writer has several addresses and wants to receive your reply at a different
place from the one from which (s)he wrote to you, for two examples.

There's nothing inherently underhanded or untoward about it and it is not
an indication of spam.