Mailflow canit be changed

Hello,

i have an issue and cannot change the mailflow settings of one of my users.

If i deactivate the mail forwarding it says that settings are updated but nothing happens.

Via powershell i get the message :

the recipient ____________ could not____________________prod.outlook.com by the domain controller can be read.This may be due to delays in replication.By existing forest mode this process should be completed successfully.

Any tips or help from anyone?Thanks!