Require users to be mailbox enabled to receive signatures

Specifies that users must have an Exchange Server mailbox in order to receive signatures.

Include nested groups when determining user group membership

Specifies that nested sub-groups should be included when determining user group membership during deployment of signatures.

Remove trailing spaces from field values when generating signatures        

Specifies that trailing spaces should be removed from field values when generating signatures; field values containing only spaces will be trimmed to empty values. For further information, see the chapter on working with fields.