Apple - Why do I get a 'connection to the outgoing server "smtp.gmail.com" failed' message in iOS Mail?
I occasionally get a call from a client of mine complaining about this. I don't know of an actual fix (or what the actual problem is) but I usually recommend doing these in order:
- Quit Mail fully: double-tap the home button, swipe up on Mail
- Normal restart: press and hold power until you get the option to shut off, wait 30s for it to shut off, press and hold power until the Apple logo shows up again.
- Try again and if it fails, forced restart: press and hold power AND the home button until it shuts off - keep holding until the apple logo shows up again
- Remove and re-add the gmail account.
Had this issue too and didn't have any joy with deleting/removing accounts and restarting my phone as @Harv suggested. Fortunately I got some help from Google's G Suite support team and they offered a solution which worked for me:
- Add the account as an 'Exchange' account
- Set the server to m.google.com (leave the domain field empty).
The underlying reason behind this (and more detailed instructions) is addressed in this G Suite help article.
Are you using a VPN? I discovered that if my VPN was set on a U.S. port, my outgoing mail wouldn't "send" from my iPhone when the phone and I were physically in another country. I switched to a VPN port in that foreign country and mail "sent" fine!