In your email client software, under Outgoing mail, set the SMTP server to smtp.gmail.com. Set the your username is [email protected] and make sure "Use username and password" is checked.

If Microsoft Outlook is unable to add Gmail account and it keeps asking for a password, you need to create an app password and use it to log in.

Gmail Pop & SMTP Server Information. If you use a Gmail email account for your business, you may wish to access it through a desktop or mobile client such as Microsoft Outlook or Mozilla Thunderbird.

The certificate problem caused issues for new users trying to send email via Gmail or Google Apps using SMTP.