Mail principal account problem

Hi
in Mail, I have a problem, i have a total of 4 accounts in Mail.
My first one is my main of course...
since some weeks, i receive emails in my 2nd account... and when i am in my first one and i do a reply, id gives me the 2nd account signature...

why ?
somebody can help me please ?

The Reply ID field is a drop down list if you have multiple accounts (I have three myself) and so you can select whichever one you want.

yes i know this... but it isn't suposse to give me the wrong account when hitting reply...