#9 Exchange Online Recipient Limit Changes

By Neil Hobson on

An organisation moving to Office 365 can consider reviewing the service descriptions that provide details on the services and features that are available in Office 365. Take the Exchange Online service description for example. It is broken down into multiple sections, providing important information for service areas such as migration options, permissions, anti-malware protection and how Microsoft provides high availability for the service.

As part of a move to Exchange Online, an organisation can also consider understanding any limits imposed in Exchange Online and how these may differ from any on-premises equivalent settings. The Exchange Online Limits section of the Exchange Online service description covers limits for a variety of service areas. One of these service areas is ‘sending limits’, which includes something known as the recipient limit.

The Exchange Online service description states that the recipient limit is the ‘maximum number of recipients allowed in the To:, Cc:, and Bcc: fields for a single email message‘. Currently, Microsoft sets the recipient limit to 500 recipients as seen in the Sending limits across Office 365 options table in the Exchange Online service description.

A common question asked when discussing recipient limits is how distribution groups count towards them. Fortunately Microsoft also clarifies this within the service description, stating that:

  • Distribution groups stored in the address book count as a single recipient
  • Each recipient in a personal distribution group counts towards the recipient limit

Therefore, an organisation that has a requirement for one or more Exchange Online mailboxes, to be able to send to more than 500 recipients in a single message would need to look at using distribution groups stored in the address book. This would then bring up other considerations, such as restricting who is able to send to these distribution groups to avoid potential misuse.

Something that caught me eye this week is that Microsoft has recently announced Microsoft 365 Roadmap Feature ID 55025 titled Tenant Customizable Recipient Limits. This discusses upcoming changes to the Exchange Online recipient limit functionality. Here’s an extract of this roadmap item:

Image: Exchange Online Recipient Limits Roadmap

This roadmap item is interesting because it covers considerations in changing the recipient limit from two different angles. Firstly, there’s the scenario to increase the recipient limit for one or more mailboxes that need to send to more than 500 recipients. As discussed above, distribution groups could be considered as a workaround in this scenario, but there are potential administrative overhead considerations with this.

Secondly, there’s the scenario to reduce the value of 500 recipients to something lower. The roadmap feature ID text discusses potential reasons why, such as a compromised user account being used to send spam emails. A UserVoice item for changing the recipient limit also shares this concern. Another reason could be to reduce the number of recipients that users are able to address in a single email message to avoid potential misuse scenarios. Interestingly, at the time of writing this post, the latest Microsoft response to this UserVoice item states that it is working on customisable limits but has no timeframes. Hopefully this item will be updated to reflect roadmap feature ID 55025.

The roadmap item text also indicates administrative configuration flexibility considerations. Specifically, while the Exchange Admin Center will be able to make single or bulk changes to mailboxes, PowerShell will be able to configure a default setting for new mailboxes, should that be a requirement. The Exchange Online administrators within an organisation will likely welcome this flexibility.

According to the roadmap, this change is scheduled for Q1 in 2020. Although this is several months away, it gives time to think about this new feature and plan any implementation.

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