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Understanding the mail limits in Live@edu


Like all well-run email systems the Microsoft-provided Live@EDU replacement for our staff email system has certain in-built limits. It is important you understand these and contact help at wbs dot ac dot uk immediately if you think they will cause problems for your work.

There are a number of different kinds of limit:

Message limits:

This applies to every message and is not expected to cause problems as it is slightly larger than the current limit.

  • Message size limit = 25MB (for comparison the current WBS limit is 20MB and University limit is 10MB). Note that when using the Outlook Web client the limit will be 10MB.

Mailbox size limit (quota)

The mailbox limit for an account is 10GB. This is a sizeable increase on the 4GB limit that most users have with GroupWise and substantially greater than the university's 0.5GB limit. Importantly however once an account reaches the 10GB limit it will not be able to send or receive any messages. It is not possible to increase this 10GB limit under any circumstances.

Recipient and sender limits:

Unlike the current WBS GroupWise system the new system will enforce a recipient limit.

  • Maximum number of recipients per message (i.e. the sum of the names in the 'To', 'CC' and 'BCC' fields) = 500. Emails sent internally may be sent to 'distribution lists'. In this case the list only counts as one recipient, even if it contains multiple addresses.
  • Maximum number of recipients that can receive email from a single account in a 24 hour period = 500. Note that separate messages sent to the same recipient each count towards the 500 limit. See below for examples of this limit.
  • Maximum number of messages per minute = 30

Examples of the recipient rate limit (taken from )

The recipient rate limit is based on a 24-hour rolling window. This means the recipient rate limit is calculated against the number of recipients that were sent a message in any 24-hour period. Here are examples to illustrate the recipient rate limit.

  • On a Monday morning, after not sending any e-mail over the weekend, you send a message to 500 recipients at 11:00 A.M. You can’t send another message until 11:00 A.M. the next day.
  • On another Monday morning, you send a message to 200 recipients at 9:00 A.M. You send another message to 100 recipients at 1:00 P.M. Then you send a third message to 200 recipients at 4 P.M. You can’t send another message until 9:00 A.M. the next day.
  • You haven't sent any messages in the last 24 hours, and then you send a message to one recipient at 7:30 A.M. You continue to send e-mail to lots of recipients during the day. If you send a message to the 500th recipient at 5:00 P.M., then you can’t send another message until 7:30 A.M. the next day.

Exchange Online also doesn’t accept a message for partial delivery to some recipients. If a user sends a message to multiple recipients, and the number of recipients for that message exceeds the recipient rate limit, the message is blocked for delivery to all recipients.How can I sent out bulk email?

Given that the Microsoft system enforces the above rules we recommend the use of the Mach5 mailer product for mass mailing. Support documentation for this can be found at