While migrating example.com subscription the following errors appear:
An error occured during mailname creation: Your key limits don't allow mailname creation: There are no available resources of this type (mailboxes) left.
Rsync failed to copy mail content from the source to the target server.
Exit code:11: No such file or directory.
Mail tab is missing under Plesk > Subscriptions > example.com.
Subscription has no service plan assigned. Mailboxes limit is set to 0 at Subscriptions > example.com > Customize > Resources.
There is no limitation for mailboxes on the Plesk license.
Insufficient number of mailboxes.
Log into Plesk as an administrator.
Note: if the access to admin account is not available, contact server administrator.
Go to Subscriptions > example.com > Customize > Resources > Mailboxes and set the proper value for a subscription.