[bdd]

Does Fastmail actually have multiple providers?

One of their mail exchangers, web site, SMTP, POP, and IMAP servers are all on the same /24, that belongs to NYI (AS11403) and according to the BGP table is not multihomed.

Historical DNS records from last two years also show they weren't changed.

I guess, "primary" is still a technically correct qualifier for the "sole" provider.

[jjeaff]

Perhaps their primary provider handles their SMTP traffic and any additional providers handle things like the cdn.