Directory and Resource Administrator 6.50
Triggers associated with the 'User Create' operation fires for the 'MailboxCreate' operation as well.
The cause of this issue is a problem in the validation process for the maibox properties. Even though the operation is MailboxCreate, the validation attempts to tie it in to the UserCreate operation.
This issue is resolved with the release of Directory and Resource Administrator (DRA) version 6.60. Upgrade to the latest version of DRA to resolve this issue.