OS X SMTP issue - Unable to send email (gmail) I have installed OS Yosemite 10.10.1 a couple of months ago. Everything was ok especially with mail. However a couple of days ago it just stopped to sending emails with no apparent reason since none configurations changes or updates have been done. 

I keep having the following error message every time I try to send an email. 

The SMTP connection to server “smtp.gmail.com” failed.
Select a different outgoing mail server from the list below or click Try Later to leave the message in your Outbox until it can be sent.

The diagnosis:


Obviously I have already checked the username and password but the problem persists.

Could someone help me to fix it please ?

Many thanks

Edit


  Following Buscar웃 hint at the comment I've gone to 'mail- pref-accounts- edit smtp -
  advanced - authentication' then selected 'none' instead of 'password'
  with was previously selected.That way it is working again.
  What are the consequences of that
  change? What exactly 'authentication' means in this context? Am I lose
  security by doing what I did ?
To make new SMTP:

Open Mail Preferences.

Click on Accounts.

If you have more than one click on one of them.

In that window look for Outgoing Mail server (SMTP).

from the pick up select Edit SMTP server.



In the new window select the (+) and enter a description (name you like), and smtp.gmail.com



Back in Account screen select that name.