Problems with email

Can someone point me in the right direction. Some members of our forum are having trouble login after they have forgotten their password. The site won’t send out an reset password email for some reason. This occurs with both gmail and yahoo emails. Is this an issue with our settings or is the problem at the other end with posters emails addresses blocking them. Does the system require a POP3 Host address for this to take place?
In addition posters cannot login using Google or Twitter is this to do with our settings as well. This is how our settings appear.

It’s likely an issue with the system sending mail. See Troubleshooting email on a new Discourse install


Thanks for that info. Another question if I can ask. Posters having issues login with their passwords. Can passwords be changed using a different device i.e. mobile app and/or can admin change a posters password via the admin panel? Is there another way a poster can login via google or twitter. But I think this requires these sites to include oauth2 and site passwords correct?

What issues?

Users can change the password on any device and can skip passwords altogether with a login link.

Yes several social logins are available: Configuring Google login for Discourse. Configuring Twitter login (and rich embeds) for Discourse