Now something that looks strange to me. We have 1 full per week, rest incrementals. As both mailbox hosts host about the same data, as expected the dedupe results of the job are quite good:

But when the full runs, it doesn't seem to dedupe at all:

This is also reflected in the .vbk file. Size of the full is over 1.1TB while there is about 600GB of 'identical' data. Now I don't see why the full job has practically no dedupe at all, as even the incrementals show that quite a bit of the changes that day can be dedupe quite well. If I have 6 days of quite good dedupe, I would expect the full backup to have at least more than 1.0.
Don't full jobs dedupe from Veeams perspective?