GMail "Send as" an O365 account

[danrneal]

This seems like a popular problem and setup that many may be looking for.

I am trying to run this proxy on a raspberry pi so doing it all with --no-gui is also a must.

My current config:

[SMTP-1587]
documentation = *** note: this server will work for both Office 365 and personal Outlook/Hotmail accounts ***
server_address = smtp-mail.outlook.com
server_port = 587
server_starttls = True
local_certificate_path = /etc/letsencrypt/live/example.com/fullchain.pem
local_key_path = /etc/letsencrypt/live/example.com/privkey.pem

[[email protected]]
permission_url = https://login.microsoftonline.com/common/oauth2/v2.0/authorize
token_url = https://login.microsoftonline.com/common/oauth2/v2.0/token
oauth2_scope = https://outlook.office.com/SMTP.Send offline_access
client_id = my-client-id

[emailproxy]
delete_account_token_on_password_error = True
encrypt_client_secret_on_first_use = False
use_login_password_as_client_credentials_secret = False
allow_catch_all_accounts = False

It looks like I finally have GMail talking to the proxy correctly.... however I'm at a loss on how to get the proxy to talk to O365 correctly to authenticate. I have an app set up in Azure with the permission "Office 365 Exchange Online | SMTP.SendAsApp| Application access for sending emails via SMTP AUTH". And I have the client_id in my config. But past that, what is my next step for getting this authorized? Current debug log:

danrneal@DietPi:~/email-oauth2-proxy$ sudo ./env/bin/python3 emailproxy.py --no-gui --debug --external-auth
2025-03-18 17:55:45: Initialising Email OAuth 2.0 Proxy (version 2025-03-14) in debug mode from config file /home/danrneal/email-oauth2-proxy/emailproxy.config
2025-03-18 17:55:45: Starting SMTP server at [::]:1587 (SSL/TLS) proxying smtp-mail.outlook.com:587 (STARTTLS)
2025-03-18 17:55:45: Initialised Email OAuth 2.0 Proxy - listening for authentication requests. Connect your email client to begin
2025-03-18 17:56:05: New incoming connection to SMTP server at [::]:1587 (SSL/TLS) proxying smtp-mail.outlook.com:587 (STARTTLS)
2025-03-18 17:56:05: Accepting new connection from [::ffff:209.85.160.172]:60706 to SMTP server at [::]:1587 (SSL/TLS) proxying smtp-mail.outlook.com:587 (STARTTLS)
2025-03-18 17:56:05: SMTP ([::ffff:209.85.160.172]:60706-{[::ffff:192.168.86.241]:1587}-smtp-mail.outlook.com:587) <-> [ Starting TLS handshake ]
2025-03-18 17:56:05: SMTP ([::ffff:209.85.160.172]:60706-{[::ffff:192.168.86.241]:1587}-smtp-mail.outlook.com:587) --> [ Client connected ]
2025-03-18 17:56:05: SMTP ([::ffff:209.85.160.172]:60706-{[::ffff:192.168.86.241]:1587}-smtp-mail.outlook.com:587)     <-- b'220 SJ0PR05CA0183.outlook.office365.com Microsoft ESMTP MAIL Service ready at Wed, 19 Mar 2025 00:56:04 +0000 [08DD663010A57B0D]\r\n'
2025-03-18 17:56:05: SMTP ([::ffff:209.85.160.172]:60706-{[::ffff:192.168.86.241]:1587}-smtp-mail.outlook.com:587) <-- b'220 SJ0PR05CA0183.outlook.office365.com Microsoft ESMTP MAIL Service ready at Wed, 19 Mar 2025 00:56:04 +0000 [08DD663010A57B0D]\r\n'
2025-03-18 17:56:14: SMTP ([::ffff:209.85.160.172]:60706-{[::ffff:192.168.86.241]:1587}-smtp-mail.outlook.com:587) --> [ Client disconnected ]
2025-03-18 17:56:14: SMTP ([::ffff:209.85.160.172]:60706-{[::ffff:192.168.86.241]:1587}-smtp-mail.outlook.com:587) <-- [ Server disconnected ]

[danrneal]

#59 (comment) helped me solve the issue. Gmail TLS won't work, need to select SSL in gmail's UI.