1,500 Recipients per day: Users can send only 30 messages per minute. If a user submits messages at a faster rate, Exchange Online will deliver the messages but will queue the messages at the server and throttle the rate of delivery.
An obscure clause in the terms of service limits the number of recipients you’re allowed to contact in a day. Small business accounts are limited to 500 1,500 recipients per 24 hours. That’s not a limitation of 1,500 recipients on one message. That’s a limitation of 1,500 recipients during a single day. And the limitation doesn’t apply to unique recipients either.
If you send a message to me and Cc: John, that would take up two of your allotted recipients. If you later in the day sent another message to just me, it would take up another recipient, even though you already sent a message to me. Unfortunately, 1,500 recipients when viewed in this fashion really isn’t that many.
Microsoft’s online documentation confirms this limitation, if you know where to look. In Office 365 help, under Recipient and Sender Limits, this is what you’ll find:
Recipient rate limit The maximum number of recipients that can receive e-mail messages sent from a single cloud-based mailbox in a 24 hour period.
- Microsoft Live@edu 500 recipients per day
- Office 365 for professionals and small businesses 1500 recipients per day
- Office 365 for enterprises 1,500 recipients per day
Microsoft claims it’s a necessary anti-spam measure:
Every online service provider must limit and constrain its service based on limitations such as the amount of disk space currently in its datacenters or bandwidth currently available and also enforce behavioral thresholds which prevent inappropriate use of the service by malicious users or criminals. This is true for any form of web-based service.
In the world of email, one of the thresholds that must be enforced is the amount of email that is sent through the system by any one user or organization in order to combat spam, mass-mailing worms & viruses. To ensure that all users experience the level of performance, email delivery expediency and client connectivity behavior that they expect, we must determine what usage typifies behavior of a spammer, for example, and put controls in place to prevent such inappropriate use. We ask customers with legitimate needs for a service that exceeds these thresholds or must go beyond these limitations to contact support so that we can best meet their specific needs.