Apple - Why do I get a 'connection to the outgoing server "" 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:

  1. Quit Mail fully: double-tap the home button, swipe up on Mail
  2. 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.
  3. 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
  4. 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 (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!