On the Settings page the email addresses have validation controlled by the config setting EMAIL_ADDRESS_VALIDATION_LEVEL . Look in config_extended.php for an explanation then copy the setting to config.php with whichever level looks appropriate.
@terryrogers It is kind of what I suggested. If you had tried disabling email validation with EMAIL_ADDRESS_VALIDATION_LEVEL then it would probably have been accepted.
But it looks like the TLDs held in the database need to be updated. That should happen automatically but you can try to force an update by setting the frequency to be a small number of days. Add or update this to config.php
@terryrogers Sorry but I don’t know.
Using EMAIL_ADDRESS_VALIDATION_LEVEL set to 0 should remove most validation. In my phplist I can update the field to the value that you are trying to use and I have EMAIL_ADDRESS_VALIDATION_LEVEL set to 3.