How does outbound rate control work for the Barracuda Email Security Serivce
By default Barracuda Email security service accounts Outbound Rate Limit is set to 150 recipients per 30 minutes per sender. That is 7200 recipients per day that any one user can send out. If your users are hitting rate limit it means they are sending out mail to more than 150 recipients per 30 minutes.
Please note that this is not a block of their mail it is a deferral. Your mail server should retry this mail until it is all delivered.
Please also note that Per User Rate Control only affects users listed in the ESS users list. Users not in the userlist are all lumped together and get the per domain rate limit which is normally 250 per 30 minutes. Anyone sending outbound mail though ESS should be listed in the userlist.
One of the reasons a sender might hit our rate control limits more than normal is the configuration of your mail server. For example: If a user sends out a mass mailing to 1000 people that will hit their rate control limit. It will take at least 4 hours for all this mail to be delivered. If your mail server retries this deferred mail every few minutes this can cause the sender to remain rate limited for a very long time. Barracuda recommends that you configure your mail server to retry deferred connections every 30 minutes to avoid this problem.
If you have mail that must go out immediately then Barracuda recommends that you either bypass ESS, sending it directly to the internet or that you use a mass mailing service that is designed for this purpose. Barracuda is also aware that some organizations use a program to mass mail that does not retry deferred mail. If you are using a program like this then we recommend that you configure it to deliver the mail directly to the internet or have it relay the mail through a fully functional mail server that can correctly handle deferred mail.
Exceeding rate control limits will show up on your outbound abuse report page however if there is a problem with your account that results in your outbound IP or a user email address being blocked you will hear directly from Barracuda via email or a call explaining the problem that requires attention.
Please reference our terms of service page in regards to bulk or mass mailing.