Introduction

Generally we have 2 main types of limits which is split into a tiered system as to what gets applied to who and what we can over-ride and what we cannot.

The following limits are in place to protect our domains, and the services we use from malicious attacks. We understand it can sometimes be frustrating however these are ultimately there to protect you, the trust and the companies from which we purchase our email services.

If marketing or mass emails do need to be sent our standard email system (Outlook) shouldn't be used, as this is subject to these limits, some of which cannot be over-ridden.

What are the Restrictions?

These limits are for an individual sending emails, and it applies to the number of recipients in the To, Cc and Bcc fields. This includes individual members of a distribution group, and includes repeated recipients.

• 1000 total recipients per day
  • This limit applies to both internally and externally bound mail combined.
  • Exceeding this limit causes the user to be blocked from sending any further emails indefinitely.
  • This limit can be reset by IT Support once it's been triggered.

• 500 total recipients per hour
  • This limit applies to both internally and externally bound mail combined.
  • Exceeding this limit causes the user to be blocked from sending any further emails indefinitely.
  • This limit can be reset by IT Support once it's been triggered.

• 100 external recipients in 1 email per user
  • This limit applies to only externally bound mail.
  • Exceeding this limit causes the email to be rejected, users account will be frozen from sending email for 15 minutes (cooling off period).
  • This limit is not controlled by the Trust, and therefore cannot be reset or overridden.

The following rule exists, but we are unlikely to be affected by it due to other rules which are more likely to get triggered:

• 150 external recipients from any mailbox in a 30 minute period
  • This limit applies to only externally bound mail.
  • Exceeding this limit causes emails to be deferred, and will be sent after a further 30 minute cooling off period.
  • Nothing gets blocked or rejected, just delayed.
  • This limit is not controlled by the Trust, and therefore cannot be reset or overridden.

For Example

An individual can send:

• One message to 500 recipients in any 60 minute period, or
• Two messages to 250 recipients in any 60 minute period, or
• Two messages to 500 recipients each in 2 separate 60 minute periods, or 
• One message to 100 external recipients in a 15 minute period, or
• Two messages to 200 external recipients in 2 separate 15 minute periods, or
• One message to 400 recipients , and One additional message to 100 external recipients in a 60 minute period

An individual cannot send:

• One message to 1000 recipients in a single 60 minute period, or
• Three messages to a total of 1500 recipients during a 24 hour period, or
• One message to 150 external recipients in a 15 minute period, or
• Three messages to 300 external recipients in a 30 minute period

Any attempt to send any more above these limits will trigger one of the above mentioned policies.

For more information, please contact cyber.security@catrust.co.uk.