Limiting Outbound Number of Recipients on MS Exchange Hub Transport

AppRiver does not support bulk e-mail. (Please note that there is a limit of 99 recipients on any message sent through AppRiver SmartHost servers.) Any message with more than 99 recipients will be refused.


If a message containing more than 99 RCPT TO: entries attempts to relay through AppRiver's SmartHost servers, the message from your sending IP address will be dropped causing mail to queue on your Exchange server and this could delay other mail from being sent out quickly. Sometimes, the dropped message remains in the Exchange Server in a retry state and it must be deleted within the Exchange server. Microsoft Exchange does not allow for only limiting the outbound number of recipients on a message, rather it allows for limiting the number of recipients on a mailbox. These settings apply to all SMTP traffic: inbound, outbound, and internal. They may be adjusted to 99 recipients. It is possible that your company may have more than 99 internal e-mail addresses that need to receive an e-mail. To remain within the adjusted limit, please create distribution groups. A distribution group is counted as a single recipient during message submission. 

Recipient Limits in Exchange 2010

Use the EMC to restrict the number of recipients per message for a mailbox.

1. In the console tree, click Recipient Configuration and then click Mailbox after that opens.

2. In the result pane, select the mailbox for which you want to restrict the number of recipients per message.

3. In the action pane, under the mailbox name, click Properties.

4. In <Mailbox> Properties, on the Mail Flow Settings tab, select Delivery Options from the list of mail flow settings, and then click Properties.

5. In Delivery Options, select the Maximum recipients check box, and then, in the corresponding text box, enter the maximum number of recipients that can receive a message from the mailbox.

6. Click OK to return to the Mail Flow Settings tab.

Recipient Limits in Exchange 2013/2016

Use the EAC to restrict the number of recipients per message for a mailbox.

1. In the Exchange Admin Center, navigate to Recipients > Mailboxes.

2. In the list of user mailboxes, click or tap the mailbox that you want to set up mail forwarding for, and then click or tap Edit.

3. On the mailbox properties page, click Mailbox Features.

4. Under Mail Flow, select View details to view or change the setting for forwarding email messages.

5. On this page, you can set the maximum number of recipients that the user can send a message to.The recipient limit is unlimited by default. If you want to specify a limit, click the Maximum recipients check box and then type the limit in the text box beneath the check box.