Keeping the Same Mail Server in a reply

• Select Mail | Preferences... from the menu in Mac OS X Mail.
• Go to the Accounts category.
• Highlight the desired account - in your case the me.com account
• Enter all email addresses you want to use with this account in the Email Address: field.
• Separate the addresses by commas (like "me@example.com,me_the_pro@example.com").

This is a workaround, not a solution...

I have not been able to replicate this behavior, except where the message has been moved from an Inbox into an On My Mac folder. Are you seeing this when in the Inbox of the receiving account?

Ernie

You can move your desired sending account to the top of your accounts list, on top of your iCloud account. That will change your default sending account.

However, as Ernie pointed out, this will not help if you move messages out of your inbox. Mail in Mountain Lion will lost track of it if you do that and default to the first account in your list of accounts.

Philip Bauman wrote:

I move all my emails out of the inbox via RULES into folders in Mail. I havce 50+ folders in the Mail program. This was not a problem in the Lion.

There is a very long thread about this issue elsewhere: https://discussions.apple.com/thread/4148125?tstart=0

This is a change from how Lion worked. No one knows if it is a bug or just an undesireable new behaviour. Apple is trying to push people towards greater reliance on Spotlight searching. Instead of complicated rules to shuffle mail between 50 folders, consider using smart folders. If possible, leave mail on the server so it is accessible on all of your devices. If you want to remove mail from the server, try using the archive feature. I just tried this and messages in my Archive folder use the correct sending account. Messges that I archive with my old hacked up system do not use the correct sending account.