how to get new message happend in source Tenant fro migrated user

Question

Hi Support, 
 
 I'm testing On Demand Migration for M365, I have migrated some users from source tenant to target tenant, some users are still in source tenant, my question is for migrated user how to access new Teams group messages which is still not migrated

Trevor Taegder · Answer

Hello pengph007 , I understand that you have migrated some users to the target tenant and that those users are now actively using their new target mailbox. However, Teams have not been migrated and Teams conversations are still active in the source tenant. During this coexistence phase, you could have these migrated users connect to the source tenant using the Teams web client, or leave their Teams desktop client connected to the source until all Teams are migrated. 
 Please let me know if you have any additional questions or need any additional clarification. 
 Thanks, 
 Trevor Taegder Senior Technical Support Engineer Quest | Support

Trevor Taegder · Answer

Hello pengph007 , 
 Currently, On Demand Migration (ODM) is only able to perform an source -> target migration of M365 Teams and SharePoint content. It is possible to perform incremental migrations over a period of time, but they should only be source -> target. 
 We are in the process of phasing out the Resource Processing feature, as it just hasn't been widely used and requires a service account that is excluded from MFA and conditional access policies. At the time of this post, the Resource Processing feature can be enabled upon request by creating a Service Request . 
 Thanks, 
 Trevor Taegder Senior Technical Support Engineer Quest | Support