That's why we're working on JMAP! Localising comes with a ton of downsides, including the fact that of the 3 other datacentres we've installed into, none have been anywhere near the quality of services that we've had from NYI over the years.

https://blog.fastmail.com/2014/12/10/security-availability/

(and yes I see another comment in this thread that I'll reply to in a second about a 1 hour network outage we had... it's the biggest outage we've had in years. Our other datacentres have had much bigger downtimes during that period)

Particularly with the increase in mobile clients that change networks regularly, we don't see a future in old school IMAP as the preferred way to access email. Please check out the JMAP working group for what we see as the future :)

https://datatracker.ietf.org/wg/jmap/documents/

So we prefer to consolidate in a few high-quality datacentres and build protocols which work well from anywhere in the world.