[jpatokal]

Are you serious? Running my small business, I used email to communicate with my coworkers, potential hires, customers, prospects, partners, potential partners, reporters, accountants, lawyers, banks, web hosts, PayPal, UPS, various government departments etc etc. Being completely cut off from that for effectively an entire business day would be destroy my ability to get anything outside "solo hacker in basement" coding done, and there really isn't a sensible mitigation plan or alternative to e-mail for this (unless you'd like to convince my bank to start posting, say, notifications of incoming wire transfers to a web form of my own design?).

[justincormack]

Your bank provides a website you can poll to find out about stuff. Not ideal, would be nice to have a proper API, but so far we only seem to be getting these for credit card payments but this is changing (eg see gocardless). For most of those things you list you could manage in an email outage, as you have phone numbers or other alternatives.

If it is that critical do you have 99.99%+ (52 minutes a year) uptime guarantees on your mail service? That is what you are asking for, and to actually deliver that (rather than an empty SLA promise) is something that very few businesses actually try to work to, especially small companies. Gmail certainly does not try to provide this.

[jpatokal]

Google's enterprise Apps SLA is 99.9%, and last year they hit 99.98%.