Authentication failure may arise due to Invalid response code received from server ( Due to error in the SMTP  Server name).So check your smtp server name is correct .And if that's right ,check your username and password.

For outgoing Sever:
Server name : smtp.gmail.com

Port: 465   

User name: something@gmail.com

Password:****

If this doesn't Work,Then you may be under proxy.

If you are under a proxy

1) Just remove your username and password and click on test connection. see if your connection succeeds

2)Then use this IP  173.194.66.109 instead of smtp.gmail.com

If still it's not working means that the port number of 465 is not opened for your IP. Type 'telnet 173.194.66.109 465' in your command line.It  should Work

Hi,

You have to allow less secure apps to access to your account. By default gmail block odoo and other apps to coonect to your account.

This may help:

https://support.google.com/a/answer/6260879?hl=en

Best regards.

For outgoing Sever:

• Servername : smtp.gmail.com
• port: 587
• username: example@example.com
• Password: "your pasword" or if you have two step verification on then use one time application password
• Connection Security: SSL/TLS

The answer to that problem is to create and use a dedicated "consumer" GMail account, without any special features.

Choosing a suitable name that clarifies its purpose might be a good idea.

Part #3 of this series might help you confirm that you are doing all that is necessary: OpenERP and Google

This working try it.

https://www.odoo.com/forum/help-1/question/incoming-outgoing-mail-configuration-44842

Don't use gmail if you have a choice. A month ago I had to update my apps that use gmail for sending email because it started to throwing not trusted device (every few days, after I added it to trusted) and they are blocking if you send to many email. So that the apps didn't crash I had enclose the email sending in a try except for smtplib.SMTPDataError and smtplib.SMTPAuthenticationError.

This to be solved by the user which is going to have the best part of the surface where they can have the information regarding the Gmail server issue which is going to solve out with particular aspects.<a href="https://supportprop58.com/windows-10-audio-crackling/">windows 10 audio crackling</a> through it will be recover the process 

Connection Test Failed! Here is what we got instead: 535 5.7.8 Username and Password not accepted. Learn more at 5.7.8 https://support.google.com/mail/?p=BadCredentials k190sm8628079pga.73 - gsmtp 

I use app passwords, but for some reason Odoo refused to connect.

My test works, its the gmail captha : https://www.google.com/accounts/DisplayUnlockCaptcha