The Lotus cc:Mail mailbox name is used to generate the alias and common-name properties for the Microsoft Exchange Server mailbox. These properties are limited to 64 characters. If any name exceeds this limit, the Migration Wizard reports an error and moves the data to the recovery file.
If your system has mailboxes with long names, the solution is to use the two-step migration method and edit the primary file before importing them. If any name exceeds this limit, you must reduce the common-name and mail-nickname fields to 64 characters. If you don't specify the mail-nickname, it defaults to the common-name.