Hi,
I have the same problem, a user has two accounts registered, one with her email as @googlemail.com and one as @gmail.com
The result is that sometimes her emails get rejected with the error:
Your reply was sent from a different email address than the one we expected, so we’re not sure if this is the same person.
I have a few other users replying by email and it only happens to this user, so I assume it’s the gmail/googlemail domain mismatch.
I am thinking of adding the alternate domain email as secondary email address on both accounts, or is there a better idea?