Zoho Mail migration failed

Zoho Mail migration failed

Got the migration process to work ok, and about 1/2 of the PST file was imported to Zoho Mail.
Received the message "migration failed"

How should we proceed?

1) Delete the messages that were imported to Zoho and rerun?
or
2) Rerun the migration wizard and assume that the additional emails will be imported without duplication?
or
3) In either case, if we delete the messages, will they be deleted from the contact they are associated with?

Thanks