Maximum Email Size

The maximum allowed size of email is 50MB including attachments.

Outgoing Rate Limits

Users who send outgoing email via the service are subject to the following rate limits. Limits (Low, Normal, High and Very High) are linked to the product which you have purchased – please refer to your commercial terms for details of which Limit apples.

Name Details
IP Address Recipient Limit The maximum number of recipients which the system will accept for delivery from a single IP address – single IP could be users home PC or a server.
Domain Sending Limit Maximum number of recipients allowed from a single domain.
Single User / Exchange Server Limit * The maximum number of recipients an authenticated SMTP user can send in a rolling hour. This limit would apply if e.g. your Exchange server is configured to send using SMTP Authentication. *

There are 4 rate limit levels Low, Normal, High and Very High the exact values can be found by logging into the control panel for your service and browsing to the mail domain’s support section

* For packages which include the Low and Normal rate limits and if using an Exchange server (or similar) to send outbound email via the service the Single User rate limit will apply. If an organisation wishes to send more than this Single User limit allows, the Package should be upgraded to one which supports High or greater limits.

100 Recipient Limit

There is a maximum limit of 100 recipients for a single email (To, CC & BCC fields). A distribution list stored in Zimbra counts as a single recipient.

Our Smarts hosts will reject any email which contains more than 100 recipients after the 100th recipient is processed. If presented with an email which contains more than 100 recipients, our Smart Hosts will deliver to the first 100 email addresses and then issue a rejection notification to the sender.

Therefore, if you attempt to resend an email which has failed because it contained more than 100 recipients, remove the first 100 (original) recipients, reduce the overall count to 100 or less and then resend the message. Otherwise recipients may receive duplicate messages.

Shortlink: