An auxiliary user is not migrated:
=|2015-11-24_11:49:39,594|I|MT|core.migrator|||| `- Auxiliary user 'email@example.com'
=|2015-11-24_11:49:39,594|I|MT|core.migrator|||| `- error: Failed to create auxiliary user on target panel. After migration customer won't be able to login with 'firstname.lastname@example.org' login to the panel.
=|2015-11-24_11:49:39,594|I|MT|core.migrator|||| u'Command user --create email@example.com -cname postmaster -role 'Mail User' -passwd ***** -company '' -phone '' -fax '' -address '' -city '' -state '' -zip '' -country '' -im '' -im-type '' -comment '' -status enabled -email firstname.lastname@example.org -owner admin -subscription-name server.example.com failed with exit code 1:
=|2015-11-24_11:49:39,594|I|MT|core.migrator|||| stderr: Wrong syntax for command's '-passwd' parameter. Validation failed. The password does not meet password policy requirements because it is not complex enough. The password must contain at least 6 characters, and it must include characters from three of the following four categories: uppercase letters, lowercase letters, numbers, and non-alphanumeric characters.
This is Plesk internal issue with id #PMT-2377 , which has been fixed in microupdate #19 .
Apply the latest Plesk microupdates .