Backup restore fails: An error occurred during mail account creation: Unable to create user to mailname. The password should be specified

Applicable to:

Backup restore fails:

PLESK_ERROR: Execution of C:\\webservices\\plesk\\bin\\mail.exe --create login@example.com -mailbox false -mbox_quota -1 -forwarding true -cp-access true -forwarding-addresses add:forwardhere@example.com -ignore-nonexistent-options failed with return code 1.
Stderr is
An error occurred during mail account creation: Unable to create user to mailname. The password should be specified.
Migration fails with the error:

PLESK_ERROR: Unable to create mail account 'john.doe@example.com' in subscription 'example.com': Command execution failed on the local server with non-zero exit code. command: /usr/local/psa/bin/mail --create john.doe@example.com -mailbox true -passwd '' -cp-access true -ignore-nonexistent-options exit code: 1 stdout: stderr: An error occured during mailname creation: Unable to create user to mailname. The password should be specified.
Mail accounts with Control Panel access but no Mailbox are not restored.

This issue has been considered as software issue with ID #PPPM-4855 that was fixed in Plesk Onyx.

Workaround for the migration if the upgrade of the target server cannot be considered:

Connect to the server using SSH.
Download and start script:

# wget https://plesk.zendesk.com/hc/article_attachments/115005789254/script.sh
# chmod +x script.sh
# ./script.sh
Restart migration