Subaddresses

We have a feature on our email service known as 'subaddresses', 'plus addresses' or 'local part suffixes'. This means you can use addresses of the form spqr1+detail@cam.ac.uk, or spqr1--detail@cam.ac.uk where the detail part is an arbitrary string chosen by you.

On a practical level this means that you can hand out different subaddresses in different situations and, if you want the messages to automatically be placed in a folder other than your inbox, you can use the detail part of the address in a filter. For example, you can use a subaddress when you subscribe to a mailing list and filter mailing list traffic using the detail part; this means you don't need to change your filtering setup if that mailing list moves. Or you can use different subaddresses when giving your email address to businesses, and when a business sells your address to spammers you can junk everything sent with the relevant detail part. Or you can set up forwarding from an old account to a subaddress to make it easier to identify forwarded messages.

Subaddresses may be used with any @cam.ac.uk, @hermes.cam.ac.uk or Managed Mail Domain (e.g. @ucs.cam.ac.uk, @ch.cam.ac.uk, @trin.cam.ac.uk and many others) address. They can be used with CRSid and with 'friendly names'. The separator must be + or --, the detail part must contain only characters in the set [a-z0-9.+-].

For example, the following would all be valid for the user with CRSid spqr1, name One User and who had, as well as an @cam and @hermes.cam address, an email address in a Managed Mail Domain botolph.cam.ac.uk.

spqr1+company1@cam.ac.uk
spqr1--company2@cam.ac.uk
spqr1+special-list@hermes.cam.ac.uk
spqr1--special.list@botolph.cam.ac.uk
one.user+detail-z@botolph.cam.ac.uk
one.user--something.99@botolph.cam.ac.uk

Using subaddresses on Hermes

By default, email to a subaddress will be delivered to your inbox. If you want it delivered into a different folder you can set up subaddress filtering rules using the Hermes webmail filter editing interface - Manage -> Filters. You can use a simple filter to Filter on Recipient:. However, for users who have more complex filtering requirements, it is also possible to use the Sieve subaddress extension (see RFC 5233) to split the local part into user and detail parts and match them separately.

A note to postmasters

Postmasters who run their own email services may wish to support this feature as well. We maintain a list of non-CS domains that support subaddresses, for which we will preserve the detail part when redirecting a subaddress to those domains. The detail part is stripped when redirecting to other domains. Please contact mail-support@ucs.cam.ac.uk if you would like a domain added to the list.