Two Gmail accounts in MacMail won't separate themselves!!

I have two Gmail accounts. One is professional. One is for crap. I use MacMail. When I send a mail from my "professional" account, it gives the receiver my "crap" address to respond to. This is not ok. I've gone into Gmail under Settings --> "Accounts and Import and deleted the other account for both Gmail accounts and have renamed my outgoing SMTP server in MacMail but am still getting the same problems. The last mail I received from a "professional" contact had the following header in her reply to me:

From: Me [mailto:the crap address@gmail.com] On Behalf Of the name I use on my professional account

Sent: Tuesday, December 04, 2012 11:44 PM

I do not want my professional contacts seeing my "crap" address! There's a few posts around about this but I've tried what they say and it's still not working. What is going on? What am I doing wrong? Would appreciate any help.

Thank you.