1. Which BEWS version you are using?
2. Which method you are using to backup Exchange mailboxes? If it is leagacy method then you will need to add those accounts manually
3. Advisable is that if you are using BEWS 11D or higher version, then disable leagacy method and start using GRT to backup exchange.
4. To backup with GRT, in the selection list simply select Information store to backup. This will backup all mailboxes available in that IS.
5. Check for the credentials of an account which you are using to backup Exchange database or mailboxes. Exchange Administrative rights are mandatory for this.

Please check and confirm. If it worked for you, Kindly mark this as a solution.

Regards,

Abhi

 Use GRT, dont do brick levels!

I am running version 12.5, using GRT and I have the information store selected backing up the first and second storage group.  Maybe it's something on the exchange server that I need to configure??

So, in the restore selections, you see all mailboxes, but these three? Any difference in configuration of these mailboxes and the other ones? Did you get the mailboxes active by sending emails to them?

Thanks

Yes, in the restore section I see all mailboxes except the 3 that I setup.  I don't really know if there is anything different in the way they are setup or not but I do know that they are all working mailboxes.

If you go to your Active directory, and check for SMTP address of these users and compare with other users, do you see some difference? Do they belong to same active directory or different? Are you checking under the correct mailbox database?

Thanks

I am also this issue with 12.5.

Roughly half the users are being backed up. Same active Directory and Data Store.

All users belong to the same active directory and all seem to have the same configuration.

Try uninstalling your license for the Exchange agent, and then reinstalling it...

Did anyone get this figured out? I seem to have the same problem: My backups run every night wihout issues, the overall size of the back up seems about right (800 GB), but when I look in the individual datastores, it shows only about 20% of the mailboxes that should be there.... the ones that are shown expand properly and everything, so GRT seems to be working for them, but why only some, not others?

And yes, this backup is going straight to tape, not to disk first..... too big...

Thanks,
Karl

Make sure you have all the hotfixes installed, there is one in particular that references the fact that BE 12.5 only shows the first 32 mailboxes of a GRT Backup on Exchange 2007.

The applicable KB article is here

Just adding this not in case someone else has the same problem in the future