"Too many proxy addresses" error when you try to add or remove email addresses from an Exchange Online recipient

PROBLEM
When you try to add or remove email addresses from an Exchange Online recipient in the Exchange admin center, you receive the following error message, where <X> represents a number that's greater than 200:
There are too many proxy addresses: <X>, and maximum supported number of recipient proxy addresses is 200
Additionally, when you view the properties of the recipient in the Exchange admin center, you may see the following message, where <X> represents a number that's greater than 200:
Warning

The object <Name of Recipient> has been corrupted or isn’t compatible with Microsoft support requirements, and it’s in an inconsistent state. The following validation errors happened:

There are too many proxy addresses: <X>, and maximum supported number of recipient proxy addresses is 200.
Note After November 2016, the error messages will change to the following, where <X> represents a number that's greater than 400:
There are too many proxy addresses: <X>, and maximum supported number of recipient proxy addresses is 400.
CAUSE
The number of proxy addresses on the recipient is more than the current limit.

To increase reliability and performance of the service, Microsoft has changed the limit on the number of email addresses that a recipient can have. 
  • The current new limit is set to a maximum of 200 email addresses per object. This limit is documented in Exchange Online Limits.
  • The limit will be increased to 400 by the end of November 2016. Documentation will be updated accordingly.
SOLUTION
The error messages described in the Problem section are cosmetic only. In other words, email messages that are sent to and received from affected recipients will continue to work as they did before the new limit was set. Therefore, administrators don't have to take any action, as recipients should not be in a broken state.

To reduce the number of email addresses for recipients who exceed the limit, do one of the following:
  • In the Exchange admin center, select multiple email addresses, and then remove them from the recipient in a single operation (before you click Save). Saving the changes will work if the resulting number of email addresses for the recipient is less than the current limit.
  • If you want to keep the list of email addresses that you're removing from the recipient, follow these steps:
    1. Export the list of addresses that's currently assigned to the recipient by using a preferred method.
    2. Use a tool such as Microsoft Excel to determine the list of addresses that you want to remove from the recipient. 
    3. Pass the list to the Set-Mailbox cmdlet as a single operation. If removal is performed as a single operation, and the resulting number of email addresses is under the limit, the update should be successful. 
If administrators have recipient objects that require additional email addresses, consider creating additional shared mailboxes and then adding email addresses to the shared mailboxes. Then, configure the shared mailbox to forward all email that's sent to it to the user’s mailbox so that users can monitor their received messages.
MORE INFORMATION
Still need help? Go to Microsoft Community.
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Article ID: 3196424 - Last Review: 10/13/2016 18:41:00 - Revision: 4.0

Microsoft Exchange Online

  • o365 KB3196424
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