Martha,
I have the exact same problem but it's not "every time", it's just sometimes.

Does it happen *all* the time for you? Let me know.

I am assuming it's some mail setting on the Mac system, but if it happens every time for you and only sometimes for me then it might be something else.

That doesn't change the fact that I have no clue

I'll forward this to our logistics group. Maybe someone will have an idea.

Kitty