What are incoming and outgoing servers for Gmail?

POP

• Type: POP
• Server Name: http://pop.gmail.com
• User Name: Your FULL email address
• Port: 995 (this should be automatically set when you select SSL/TLS)
• Secure connection: SSL/TLS
• Secure authentication: normal password. (OAuth2 is not supported by Gmail for POP accounts)

IMAP

• Type: IMAP
• Server Name: http://imap.gmail.com
• User Name: Your FULL email address
• Port: 993 (this should be automatically set when you select SSL)
• Secure connection: SSL/TLS
• Secure authentication: normal password or OAuth2 (recommended)

Set tools -> account settings -> server settings -> advanced -> IMAP server directory to [Gmail] to fix problems with how it lists folders in the folder pane.

SMTP

• Server Name: http://smtp.gmail.com
• Port: 587 (you could also use port 25 if your ISP doesn't block it)
• Username: Your FULL email address
• Secure connection: STARTTLS
• Secure authentication: normal password or OAuth2 (recommended)

Don't configure Thunderbird to save a copy of any messages you send in tools -> account settings -> copies & folders. Gmail's SMTP server automatically saves a copy of any message you send in the Sent Items folder for you.

The SMTP server also supports using port 465 with SSL/TLS.

—mozillazine.org