mail being sent twice from different accounts

I have noticed within the last month or two that when I send mail I get responses from the mail on a different account then what was sent. I took a closer look today and found a little more detail to make this even odder.

I have numerous email accounts set up on my Macbook Pro running Yosemite (10.10.5). My mail settings are set to send mail from the account of the selected mailbox. Not sure if it makes a difference in this discussion, but my personal account is listed first, my work account 2nd, and various other accounts after that.

Today I received an email from a friend, so I was reading that in my personal account, and hit reply, composed a message, and sent it. When composed the outgoing message showed it was from my personal email. About an hour later I got his reply, but it landed in my work email account. When I viewed that email, both the header of the message, as well the From field in the header that was automatically copied from my message to him showed my work email as the sending email. I then went into my sent mailboxes and the exact same message shows it went out twice - once from my personal email and once from my work email. I contacted the recipient and he only received the message once - from the work account.

Anyone experienced behavior like this?