FastMail is now signing all outbound email with a DKIM signature. DKIM is a way of validating the source of an email and is being more and more widely deployed.

This shouldn’t affect users in any way, it just means that emails being sent through FastMail’s servers can now be certified as having gone through FastMail’s servers, which will help in spam feedback complaints and protecting the sending reputation of FastMail’s servers.

For technical users, with DKIM, you need to specify a signing domain, and we’re using our generic domain rather than,, etc.