Sender Rewriting Scheme (SRS)

Forwarding email in the modern world

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Many mail systems now filter mail based on Sender Protection Framework (SPF). This provides some protection against phishing attacks as it makes it harder for an attacker to send a fake email purporting to come from another organisation, such as a bank. SPF is now used by all the popular webmail systems to protect their users from such fake emails. This includes Gmail, Hotmail, Outlook, Yahoo, and many others. Incoming email that fails their SPF checks will generally be filed as spam, or simply disappear without trace.

A downside of SPF is that it does not permit the traditional way of forwarding email, as used by our mail system. This means that if you attempt to forward email from a domain hosted with us to an account at one of the popular webmail sites, it will not arrive reliably.

The Sender Rewriting Scheme (SRS) offers a solution to this problem. It alters the sender address to use your own domain, which means you control the relevant SPF records. You can ensure that your forwarded email passes SPF checks by spf for your domain.

It should be noted that SRS changes the sender address, which is not normally visible to the end user. Emails contain a separate from address, which is what is typically displayed, so SRS generally has no user-visible impact.

Hosting accounts on lynx, onza, and yali

For all our standard hosting accounts, SRS can be enabled in the control panel. Simply tick the box “Enable Sender Rewriting Scheme (SRS)” when you create the forwarder on the “Add delivery action” page. Or you can convert an existing forwarder to use SRS by ticking the same box on the “Edit delivery action” page.

Custom Exim filter files

If you are using a custom Exim filter file, you can use this command to forward with SRS:

pipe "srs-forward a.n.other@example.com"

Sphinx accounts

In order to use SRS on domains hosted on sphinx, the configuration for the domain must first be updated to a new format. This is currently a manual process; please email us with the name of the domain and we'll be happy to set it up.

Redirect accounts

SRS is available for Redirect accounts, but it cannot (yet) be configured through the control panel. If you want to enable SRS for a Redirect account, please email us with the details of which email addresses you want it for, and we'll be happy to set it up.