Could it be that the person has the email address saved as the default contact method in their contacts?
For a bit of time I had no cell service, but people could use Messages to send to my email address for my iCloud account. Once cell service was restored to the device, messages from one person always came addressed to the email while everyone else reverted to the phone number. I just assumed that this person's contacts listing for me was updated, or possibly even a separate contact using just my email???? I never figured it out/confirmed it either
They talked about it on the accidental tech podcast years ago when someone emailed him with the solution to this problem which one of the hosts was having.
I’ve tried searching but I’m unable to find which episode it was since search engines don’t work anymore.
So here’s what I think it might be based on what little I remember. When messages you’re sending are going to the wrong address, I think what you…
1. Tap the contact pic at the top of the iMessage thread
2. On the first row of buttons, tap the far right “info” button with a generic contact poster icon
3. Tap the “message” link
4. All their iMessage addresses will pop up, choose the one you want to use
I think that might “move” the thread to the right place.
I know in your case it sounds like it’s the other party who would need to do this. If this doesn’t actually do anything or create a second thread, I’m sorry. I know there’s a way I just don’t remember it if it’s not the above.
