SMTP seems to truncate domain extension

[dehy]

I have created a new user on the admin panel, with an email with a long extension (ie. mydomain.digital).

The user is correctly created but the end user did not receive the email.

I looked at my transactional mail service logs and it seems it received smtp request with the recipient address truncated to the last 4 characters (ie. [email protected]), thus unable to deliver.