Problem sending emails from specific gmail account
There are two places in Mail preferences you should look at.


One is the Composing Tab


In the make sure you do NOT have selected send from Account of Selected Mailbox, but have the Account of your choice selected.




The second one is in the Accounts Tab.


Again check your settings here, and once you have selected the right account then check the use only this account.

This you have to repeat for each account.