the question is as follows. We have organized a mailbox migration from exchange 2019 to zimbra 9.0.0.0_GA_4546.NETWORK via Imapsync. The migration is done using the following command:
#imapsync --pidfile /data/maildb/imapsync/pid/accoun1 --host1 exchange.host.com --user1 [email protected] --authuser1 [email protected] --password1 "***********" --authmech1 PLAIN --nosslcheck --host2 zimbra.host.com --user2 [email protected] --authuser2 [email protected] --password2 '**********' --authmech2 PLAIN --useheader Message-Id &
Accordingly, to increase the speed of migration of all the boxes, we run the processes in parallel:
imapsync --pidfile /data/maildb/imapsync/pid/accoun2... imapsync --pidfile /data/maildb/imapsync/pid/accoun3... imapsync --pidfile /data/maildb/imapsync/pid/accoun4... etc.
This method is probably the only option for mass mailbox migration, which we discussed with the imapsync developer himself. In our case everything works, but the problem is that we can't run more than 16 simultaneous migration processes because Exchange doesn't allow more sessions. The problem, as I understand it, is the "Default number of user sessions per mailbox database" values for the following lines: Availability service, Exchange ActiveSync, Exchange Web Services, Management, MSExchange Remote Procedure Call, Outlook on the web (formerly known as Outlook Web App), POP3 and IMAP4 Others (for more details: https://learn.microsoft.com/en-us/exchange/architecture/mailbox-servers/managed-store/managed-store-limits?view=exchserver-2019).
Now the question is how to remove these restrictions for one specific account? In our case we have an admin account "[email protected]" which has access to all other user mailboxes and through which the migration process takes place. Of course, we can migrate 16 mailboxes each, but this limits the whole process.
Also, it is possible that this process can be changed via EWS/ThrottlingPolicy, but it is not quite clear how best to do it and whether it is relevant to our problem at all (source: https://learn.microsoft.com/en-us/exchange/change-user-throttling-settings-for-specific-users-exchange-2013-help).