Outbound Rate Control
Important
Senders and IP addresses cannot be exempted from Email Gateway Defense outbound rate control.
Outbound rate control protects against spam and mass-mailing malware from compromised accounts. It also protects Barracuda systems and customers from abuse originating from compromised senders. When limits are exceeded, messages are temporarily deferred (delayed), not permanently rejected. These limits apply to outbound messages sent through Barracuda outbound mail servers.
Overview
Outbound rate control does not permanently block outbound mail. When a limit is exceeded, Email Gateway Defense (EGD) defers mail. Your sending mail server will retry delivery automatically.
If you need additional guidance, contact Barracuda Networks Technical Support.
Outbound rate control limits vary based on whether a user is managed or unmanaged.
Unmanaged user – A user that does not appear in the Users List.
Managed user – A user that appears in the Users List.
For details, see Understanding User Accounts | Default User Settings.
The outbound rate control limits for managed and unmanaged users are tracked separately, and their limits are completely independent.
How emails are counted is based exclusively on the number of recipients one or more emails are sent to, not the sending IP address.
Large recipient lists (more than 100 recipients) – While there is no hard recipient limit in EGD, the service will process the first 100 recipients and defer the rest. The sending server will then try to send the message to the next 100 recipients. This continues until the message has been sent to all valid recipients. Barracuda Networks recommends splitting the message into batches of fewer than 100 recipients. Each batch is effectively treated as a new message. See also Message Deferral and Recipient Limits.
The outbound rate control limit does not include internal (intra‑domain) emails. It is only for messages that are sent through Barracuda outbound mail servers.
Unmanaged Users
The default outbound rate control limit for unmanaged users is 12,000 recipients per domain (combined across all unmanaged users) in a rolling 24-hour period.
This is a single limit for outbound email from all unmanaged users within the domains registered in the account who are not in the Users List for that account.
This limit does not impact limits applied to managed users.
Managed Users
The default outbound rate control limit for managed users is 10,000 recipients per managed user in a domain within a rolling 24-hour period.
This is a per-user limit for users that exist in the Users List of the account.
This limit does not impact the outbound rate control limits of other managed or unmanaged users.
Bulk Mail
If you have bulk mail that must go out immediately, you can either bypass EGD or use a mass mailing service designed for this purpose. If your mass mailing service does not retry deferred mail, Barracuda Networks recommends configuring the service to deliver the mail directly to the internet or relaying the mail through a fully functional mail server that can correctly handle deferred mail.
Exceeding rate control limits is shown on your outbound abuse report page. If there is a problem with your account, it may result in your outbound IP address or a sender's email address being blocked. Barracuda Networks will contact you via email (or by phone if an IP block is approaching) to explain the problem and what action is required.
See Barracuda Networks Cloud Service Terms for terms of service regarding bulk or mass mailing.
If the default maximum outbound rate control limit for managed or unmanaged users needs to be lowered to meet your needs, contact Barracuda Networks Technical Support.