Mail Sending from Wrong Account

[undertheweather]

I have 2 email accounts set up in Mail. When I send an email from Account A, it shows up in the "Sent Mail" tab as having been sent from both accounts. When the recipient opens the email it appears to have come from Account B. When they respond it sends the response to Account B.

Any ideas what's going on? I have OS X 10.9.2 on my computer.

 

[undertheweather]

Problem Resolved:

In preferences the server for that account was offline. I had to enter the password for that account to bring it online.