I have a very tiny personal site with Hostinger and have had a bit of email downtime this weekend which was fairly annoying.
If I migrate to something like Hostgator, any clue on what kind of downtime I’d be looking at? Support’s answer was “it depends”.
Going through job hunting right now so would hate to miss (another) important message from a recruiter. I could always use a temporary professional gmail for a few days as a backup.
Honestly spending a bit of money goes a long way in my experience. Since I started playing with VPS I ended up hosting a few small static sites for friends and their businesses, but email was always a bit of a problem. DIY is super time consuming and potentially VERY dangerous if neglected, and shared hosting email always sucked.
Most of them settled on either iClouid+ for 1$ a month or non-Apple users went for some Israeli mail host, still about a dollar a month.
~4$ buys you hosting from Microsoft or Google and they do have better anti-malware built-in.
Yeah was looking at protonmail and tutanota as a more permanent solution. Would need to switch hosts, looks like a ~12 hour propagation in which the address should work fine. Will probably do this next Saturday.
In the future need to transfer the domain ownership from Hostinger to namecheap or something as well, possibly more down time for that?
Switching MX record doesnt cause downtime per se, your mx record query will always return an IP, the trouble is that for a certain amount of time (the 12-24 hours mentioned above) some servers may go to either the old or the new service depending on the state of the records.
What can happen is that incoming messages may be routed to either of the two servers in that period of tie so you would end up with a ‘split’ situation where you have part of a mailbox in one place and part on another. Also, there is the problem of syncing mailboxes if you’re using IMAP/365/whatever keeps a copy of the mails on the server
There is no ‘proper’ way to avoid that, one that works when migrating to 365 is to do it in phases, where during the initial phase you set up 365 to accept emails for a given domain, but you also set up a rule that forwards any email received for some/all recipients to the old servers.
Then you switch MX records and keep using the old one with the forward until things have settled
Then you sync the mailboxes to 365 and disable progressively the forwards, and start using 365/the new service …
This could be feasible with other third party services as well, as long as they are flexible enough to support these type of configurations … and as long as you know what you are doing 
If the TTL on your email A, TXT, and MX records is set low there will be no downtime.
There could be downtime if attempt to change name servers and hosting providers at the same time. If Hostinger allows you to use an external DNS provider, I would transfer the domain before changing your hosting. Cloudflare offers free DNS services for personal use.
They sucked when I used them +10 yrs ago. Can’t imaging they got any better 