SMTP seems to truncate domain extension

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. user@mydomain.digi), thus unable to deliver.

Reproduce the admin-panel user creation flow with an address such as user@mydomain.digital, then inspect the transactional mail service logs and the SMTP request. The fix is complete when the full recipient address is preserved and the email can be delivered to domains with long extensions.

Written by the indexing model from the issue text.