FastMail changelog update

The following changes have been rolled out to production:

• When you use FastMail’s nameservers for your DNS, one of the default
  records we publish is an SPF
  record. Until now, we’ve published this as a TXT DNS record type
  and a SPF DNS record type type.
• SPF DNS record types have been deprecated
  (http://tools.ietf.org/html/rfc7208#section-3.1) for a while, so
  we’ve now removed the SPF DNS record type and are only publishing
  TXT DNS records types.
• This shouldn’t affect anyone, but we’ve put up this post as
  informational for anyone experiencing some
  issue with ancient software or systems.