Post-import, numerous users are in Suspended state in Discourse because their phpBB email address has a trailing space. The user summary pages have this message:
This user is suspended.
Reason: Invalid email on import
While it would have been nice for phpBB to prevent this, it’s too late now.
A potential simple solution is for Import to trim whitespace from the start and end of email addresses during import.
If the import code is common to other originating platforms, the misbehaviour could also be common.