Email Integration

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The hornbill platform can operate as an enterprise class stand-alone email system or can integrate with your corporate e-mail infrastructure

Protocol Support

The Hornbill platform has comprehensive support for all open industry standard protocols. For details please see the E-Mail Protocol Support

Sending Email from a custom domain

Because Hornbill is a cloud solution, when sending e-mails from your Hornbill instance, you may want to send those e-mails from your corporate domain rather than a sub-domain. There are two configuration possibilities to achieve that

Using the Sender Policy Framework (SPF) standard

This is the most straightforward scheme to implement, you simply add your domain to the hornbill instance and ensure the your DNS includes a directive in your SPF policy to tell mail servers out there that you are authorising mail messages coming from our servers to be from - because of automated SPF checks done by our servers during configuration this can easily be set up by our customers without our assistance.

Additional reference Documents

Using SMTP Smart Host

Instead of our servers taking care of mail routing, we can instead simply route all outbound e-mails for your specified domain to an SMTP relaying server of your choice. Typically this is your own enterprise SMTP server which you have to provide us access to (generally by creating special firewall rules to enable our servers to connect.


This is known as Forward-Confirmed reverse DNS (FCrDNS). This basically means that the hostname's A record must match the reverse DNS (PTR) record for the IP (and Vice Versa) . This was a historic attempt to ensure that the Sender owned the domain and the DNS record. In reality it never really worked once cloud services or multi tenant systems became a reality with multiple SMTP serves serving many customers and having resilience and was dropped by all but 2 lists years ago.

Therefore as with many other cloud vendors, we are advising our customers and their email recipients to avoid using any blocklisk that implmennts FCrDNS or if not possible configure Hornbill to use their own SMART host rather than the provided SMART HOST