Error: Unable to open this mailbox.
This error indicates that the Source returned a folder which could not be opened. The term "mailbox" is confusing: in IMAP technical terminology, a mailbox is actually a folder.
There are different reasons why you may receive this error:
- The user deleted, renamed, or moved the folder while the migration was in progress.
- The folder has special characters or spaces, causing the IMAP system to fail when trying to open the folder.
- The folder is a special system folder (i.e., anti spam folder) which can never be opened.
We recommend the following:
- Check to see if the folder still exists with the same folder path.
- Check to see if the folder contains special characters, or looks like a "special" system folder.
- Consider filtering the folder.
- Resubmit for migration.