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SPF records for mail domains under

SPF records are entries in the DNS that describe which mail servers are permitted to send email 'from' a mail domain.

The standard SPF records that we publish for most mail domains under the domain say that mail is permitted from the entire CUDN IP address space and Microsoft Office 365 Exchange Online.

Other IP addresses are marked "neutral" (i.e. neither positively permitted nor explicitly forbidden).

Specifically, our standard SPF record is: TXT "v=spf1 ?all"

The SPF record published at covers the whole CUDN. This name is also used for incoming mail via the central mail relay. We re-used this name for SPF because it is conveniently short and mail-related.

Despite the name, the SPF record covers the entire CUDN and is not specific to the central mail relays.

Please let know if you need any changes to your mail domain's SPF record, or if you want an opt-out.
If you are using one or more off-site mail service providers, we recommend that they are set up on provider-specific subdomains (

This is because there is a strict limit on the size and complexity of SPF records, and we want to avoid hitting that limit. We can help you with setting up subdomains for mail service providers - please contact

For more information about SPF records, see

Last updated: 26 January 2018