This may work... Mail > View > Customize Toolbar allows you to add an "Add To Contacts" icon to your toolbar, and that should tell Mail that mail from that source isn't junk.
Don't forget that your IMAP or POP server or even some intermediate server can flag a message as suspected junk and Mail's Junk Mail filter recognizes and by default honors that flag. This can be disabled inMail > Preferences > Junk Mail by UNchecking Trust Junk Mail headers in messages.
I’ve done both of these and something worked. I had the Sender send me a test email, which arrived and went straight to the Inbox.
In my case, when it does not, I see "Move to Inbox" as an option. Do this and it should be seen as non-junk in the future.
That was one of the first things I tried but, in my case, it didn’t deliver the desired result.
In the meantime, consider the excellent spam filtering software
SpamSieve.
I will try as because the “…whitelist to guarantee messages from previous correspondents are never marked as spam.†is interesting. However, I’m also wondering if the ISP’s filtering is the issue in which case I assume it’d be before SpamSieve could act.
I intend to talk to the ISP technical help tomorrow.
