Our Email Migration app is only able to migrate emails that are visible in IMAP. Please ensure your email folders are visible in IMAP before migrating email.
For example, in Gmail to ensure your emails are visible in IMAP:
First, within Gmail, go to Settings > Labels. For your messages to migrate, the “Show in IMAP” option must be checked for the respective email's label.
Second, within Gmail, go to Settings > Forwarding and POP/IMAP. Under the “Folder Size Limits” option, make sure that “Do not limit the number of messages in an IMAP folder (default)” is selected.
Once the messages you wish to migrate are visible in IMAP, begin a new migration to transfer the newly visible labels/folders and emails. None of the emails that were previously transferred will be duplicated -- only newly visible emails and labels will be transferred in subsequent migrations.