Hi,
I would be tempted to try and exclude the iPhone from the picture.
On the iPhone in Settings Sign Out of the Apple ID in Messages > Send and Receive
Then slide the Messages active Button to Not active in the main settings page for Messages (which turns It off).
On the Mac if it showing two options in Messages > Preferences > Accounts > iMessages Account and the Receive At section then make sure the "Start Conversations From" drop down is selecting the Apple ID.
Now try and iMessages someone.
Does this work ?
If it does not work then open a Finder window and Hold the ALT key down whilst using the GO Menu and select the Library that appears
Navigate to the Preferences Folder.
Find the com.apple.ids.service.com.apple.madrid.plist file and drag it to the Trash.
This file holds the Apple ID and any Receive At alternatives.
Restart Messages and you will have to re-enter the Apple ID and password again.
Now try sending an iMessage again. (See Note 1 at the bottom)
If that works Enable the Messages app on the iPhone and wait until it says the Number has Verified.
When it has done that send a test iMessages to your Apple ID.
If that works reply and then if that has worked add back the Apple ID.
This will cause the Pop up to reappear on the Mac to say what the iPhone is using.
Accept this.
What this will have done is forced the Mac version to reconnect to the iMessages server as well as the iPhone to do the same.
In addition the iPhone will have been forced to redo the Sync link to the Apple ID. (which you then will have had to accept on the Mac)
NOTE 1
If the Mac fails in Messages at this point - either in Registering in the first place, not finding a contact and saying they are Not Registered or Saying the iMessages is not delivered - which are all symptoms of not logging in properly then the only recourse is to Contact Apple Support.
State you have an Apple ID issue (It relates to using iMessages only and also Only from your Mac).
Apple ID issues are free to fix.
The Apple care first level responders are Script Led trying to fix Apple Care issue. (They are trying to get to to test Hardware and Software and not deal with Apple ID issues)
Ask to speak to a Level 2 person.
These can still not know of the issue about some Macs triggering the Server to not use the Apple ID.
Others know but want to gather data so that the engineer can figure why this gets triggered.
Some of this is OK.
Updating, Upgrading or Reinstall the OS will not change things.
Be persistent in trying to get them to reset the server.
When people report back on this they say they are told it will take 24 hours
I can't say we have found a quicker way to get though the Apple Support team process or in trying to get them to speed up the reset process.
![User uploaded file](https://discussions.apple.com/content/attachment/702375040)
7:49 pm Friday; April 15, 2016
iMac 2.5Ghz i5 2011 (El Capitan)
G4/1GhzDual MDD (Leopard 10.5.8)
MacBookPro 2Gb (Snow Leopard 10.6.8)
Mac OS X (10.6.8),
Couple of iPhones and an iPad