The OAuth2.0 protocol allows the connection to the SMTP mail server of Google, after acceptance of the connection authorization, by exchange of tokens.

The revocation takes place in the management of: Application associated with your account

No more password is stored in LibreOffice.

• LibreOffice 5.3.3.2 - Lubuntu 16.10 - LxQt 0.11.0.3

• LibreOffice 5.3.1.2 x86 - Windows 7 SP1

I encourage you in case of problem to create an issue I will try to solve it :-)

• Smtp Server: smtp.gmail.com

• User: your gMail email address (mandatory)

• Password: your gMail password (needed for Login/password authentication, not used with OAuth2 but do not leave empty)

• SSL on port 465

• TLS on port 587 (recommanded connection type)

• Login/password with SSL or TLS

• OAuth2 with SSL or TLS (recommanded authentication type)

Load: Google Account Setting

You must enable less secured application.

You must get authorization code from Google:

LibreOffice - gMailOOo wants to Send email on your behalf for sending email

copy and paste authorization code to LibreOffice gMailOOo Message Box.