Rate Limits

Administrators have the option of setting rate limits on outbound mail on a per-user basis. Rate limits set the maximum number of outbound messages each known user, and the total of all unknown users, can send per hour. You can also limit the number of recipients users can send to in a six (6) minute period.

Rate limiting is primarily a means of preventing users from knowingly or unknowingly sending out spam blasts, which can result in your IP address becoming blacklisted. If a user exceeds the messages-per-hour or recipients per-six-minute limit, mail is not accepted by theEmail Security product, with either a 451 (temporary) or 550 (permanent) error code.

Notes:

(1) If the outbound mail is load balanced between multiple mail exchangers, the limit applies to each exchanger. Therefore, the effective limit will be the configured rate times the number of outbound mail exchangers.

(2) If rate limits are turned on for an individual user but turned off for the domain, the system default error messages are used if an error is encountered.

(3) Blacklisted senders are not counted against the message rate limits.

Once outbound filtering has been configured, rate limiting can be configured as follows:

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System administrators: Can enable or disable rate limiting, specify rate limits per mailbox that override the default settings for the Outbound IP, enter the maximum permitted number of messages per hour (1 – 99999) and six (6) minute period (1 – 99999), select the type of error code returned to the mail server (451 or 550), and enter the text of the error message. By default, rate limiting is disabled. Known senders can be exempted from rate limiting.

Note: Outbound messages that receive 550-series errors can be sent to the administrator for review.

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Hosted administrators: Can configure message rate limits but not disable them, and select the maximum permitted number of messages per hour. Options are 100, 200 or 300. They can also select the type of error returned to the mail server and enter the text of the error message. By default, the limits are set to 300 messages per hour for known and unknown senders. The recipients limit can be enabled/disabled and configured by entering a value in the respective text box.

To add rate limits to outbound mail:

Manage >> Outbound IPs >> {Outbound IP}

Select which rate limits to set.

Messages per Known Sender	Enter the number of messages you want to accept per hour for each single known sender. To exempt known senders from rate limiting, select the Unlimited checkbox.
Messages per Unknown Senders	Enter the number of messages you want to accept per hour for all unknown senders. To exempt unknown senders from rate limiting, select the Unlimited checkbox.
Recipients per Sender	Enter the number of recipients per sender you want to accept per six (6) minute period. To allow unlimited recipients per sender in a six minute period, select the Unlimited checkbox.

Note: An alias email address is considered an unknown sender.

For each rate limit you are using, select the error to return when the limit is exceeded.

451	Temporary
550	Permanent

Type the text of the error message returned to the mail server when the limit is exceeded.