Sending with CloudMailin Outbound

Our outbound product is newer than our inbound product and is still evolving. Although it's being used in production by a number of customers we'd greatly appreciate any feedback you may have. As always just contact us if you have any feedback.

Getting Started

If you have any questions at all please contact our support team using ou contact us page.

Transactional email

The CloudMailin outbound system only allows you to send transactional messages. Marketing or bulk messages are not permitted. If you're not quite sure here are some examples of transactional message types:

  • Welcome Messages
  • Password Reset
  • Receipts / Invoices
  • Comment Notifications or Replies

Daily, Weekly or Monthly Digests and updates sit in a bit of a grey area. At present we are permitting this type of message. However, they'll need to be marked as digest messages. See Queues / Priority.


There are a number of limitations we'd like you to be aware of. If any of these cause an issue please contact us.

Title Description
Recipients Messages are currently limited to a maximum of 20 recipients.
Message Size The maximum message size (unless otherwise agreed) is 10 MB this should include all message content and encoding.
Attachments Attachments are limited to safe formats. We do not allow executables or those often associated with viruses. Although not exhaustive the following attachments are not permitted vbs, exe, bin, bat, chm, com, hta, pif, reg, vbe, vba, msc, msi.
SPAM We will run automated SPAM checks against messages. Those with a high score will be rejected.
Max Volumes We will help you to automatically ramp up sending volumes, starting small and growing the number of emails you can send per day. Please contact us if you have any questions about this.
Bounce Rate Bounces and supressions will be monitored. Because we're sending transactional email we don't expect this rate to rise above 2%. We can help you to ensure this is successful.

Please contact us if we need to work with you on any of these limitations.