Sharing between domains?

Hello Community,

I am facing the following question: how is it possible to share malboxes between domains?

Example:

• 2 domains present on the same dovecot: domA and domB
• userA@domA
• userB@domB

userA@domA wants to share his mailbox to userB@domB (again same server)?

Thank you for your help.

Greetz