Any Work arounds for not being able to share mailboxes across Multi-Tenant Organizations?

Hi,

Thanks for your response

I'm aware that you can't access mailboxes cross-tenant even with an MTO, which is why I specifically asked for suggestions of "next best thing". To word it another way, in a situation where a shared mailbox WOULD have been the ideal solution (if it was possible), what approaches have people used instead to tackle the situation in an MTO, preferably ones with the least kludging necessary.

With regards to your specific suggestion, MTO synched users are already members in the destination tenant, can I assign an exchange license to that account to allow shared mailbox access or do they require a separate account on that tenant?