Thursday 22 September 2016

Validating email addresses for Exchange recipients before migrating to Exchange Online

This is now set to 400 from 200 as per this Microsoft article here. I've updated accordingly.

Recently Exchange Online has added a limit to the number of proxy addresses (email addresses) an object can have (mail enabled user or mailbox for example) in Exchange Online.

This has gone from a seemingly unlimited number to "400".

This poses a problem for any migrations, Hybrid or otherwise, where an on-premises mailbox has more than 200 email addresses assigned to it.

Microsoft has published this limiting change, although buried, here.

So before migrating to Exchange Online it may be wise to check for any recipients that have more than 200 email addresses; you can then resolve the issue and have a better migration experience.

To check:

Get-Recipient | Where {($_.EmailAddresses).count -gt 400}

In the example below I have used 'Get-Mailbox', but this is only to limit the number of returns for this blog post example. The first shows the command, the second shows the command bringing back any mailboxes with email addresses of more than 10, and finally in the third I am getting the all clear as none have over 200.

If you have over 1000 objects don't forget -ResultSize!

Get-Recipient -ResultSize unlimited | Where {($_.EmailAddresses).count -gt 400}

Have a great week!

Oliver Moazzezi
Twitter: @Olivermoazzezi

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