We have a office 365 hybrid set-up with an Ex 2010 SP3 environment. All traffic is routed through the on-premise exchange.

One user, whose mailbox is hosted on 365, wants to mail ~300 people at once. Their 365 mailbox is configured to allow 500 recipients however when the user sends to 300 recipients, he receives a bounce back from the on premise server stating that the limit is set to 30. This is true as our default is set to 30 in the transport settings of the exchange server, however we don't want this to be increased across the board.

Is there any way we can allow this one user to be send to 300 recipients through our exchange server without increasing the default for all users?



You might wish to come up with a new Client Throttling Policy for that special user and then inside that Client Throttling Policy adjust the values for (see here):

The RecipientRateLimit parameter specifies the limits on the number of recipients that a user can address in a 24-hour period.

and if needed:

The MessageRateLimit parameter specifies the number of messages per minute that can be submitted to transport by POP3 or IMAP4 clients that use SMTP. Clients receive a transient error if they submit messages at a rate that exceeds the value of this parameter. Exchange attempts to connect and send the messages at a later time.

  • Thanks for the suggestion Bastian however this won't change the number of recipients that the user can send to at any one time. – Z Holt Dec 1 '17 at 9:50
  • Yes and no, the idea was here to adjust the default throttling policy to something you need (e.g. 30) or better build a new one for all users (so you do not change the default policy). This will then restrict anybody to the current values you have on the connector. Then build a new one with a higher limit and also adjust your exchange connector. This will then restrict all users but not the one who need to send more emails and the connector will not block him. – BastianW Dec 5 '17 at 20:47

Are all of those recipients internal? You can just create a distribution group and mail that group address. If it's a mix of internal and external, you can still do this but you have to create the external contacts in Exchange and add them to the group.

Another options it to create a transport rule and connector and route the mail directly to the internet (and not your internal Exchange server). You can create a rule that uses some trigger to route those specific messages to the connector.

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