Apple Mail

MBPro on OS 10.12.2

MAIL
Version 10.2 (3259)

Since the update to OS 10.12.2 have noticed an annoying quirk when sending emails.

With zen internet, for many years, I have used my normal email address such as "[email protected]".
I also have a POP3 email address, "D" for which I pay extra.
I try to keep emails [IN and OUT] on various projects/topics stored in a folder for one of several email addresses.

When I compose an email I get the option to choose the sender email address from a list called FROM.
The list contains my 3 email addresses
For some reason, now after the OS update, the sender is often wrongly displayed on the sent email as "[email protected]", even though I have deliberately chosen from the list the POP3 "D" address as sender/FROM.

Has anyone else had this sort of peculiarity?
At the very least, this causes some confusion to the recipients of some of my emails, when they choose an email address for their replies to me.

Any ideas?

I've found that it choose the smtp server for the account you happen to be clicked on (ie the on that you can see the list of messages for).

It is probably worth checking the account preferences to make sure that they are all set up properly, because I don't think it handles defaulting that well.