APPENDIX

# SPDX-License-Identifier: GPL-3.0-or-later
# Copyright (C) 2019--2022 Junjiro R. Okajima

XOAUTH2-PIPE

Appendix

Contents
A  Add more Gmail accounts
B  Support more protocols
C  MUA setting
----------------------------------------

A Add more Gmail accounts

If you have multiple Gmail accounts or there is another user who has a
Gmail account on your system, then you may want to make more users
able to relay to Gmail directly.
It is easy, just add his account and refresh-token into USER_FILE.

 *  Run "xoauth2-rtoken <web_browser_command>".

  In the web browser, login using another Gmail account and allow
  xoauth2-pipe to work on the e-mail on that Gmail account.  The owner
  of Gmail account should do this.

 *  As a result of allowing, the screen will show you another
    refresh-token.
 *  Manually copy/paste the refresh-token to the file USER_FILE.  Or
    ask your system administrator to do so.  Note that the
    refresh-token should be kept in private.  The file USER_FILE is
    not world-readable.

  ----------------------------------------
  another-account@gmail.com:<another refresh-token>
  ----------------------------------------

B Support more protocols

Currently xoauth2-pipe supports SMTP only.  If you want more protocols
to support such as POP3 or IMAP, then try these steps.

 (1)  Make it clear when and how AUTH command should be issued in the
 session/conversation.

  For example, in SMTP session, xoauth2-pipe intercepts MAIL FROM
  command and inserts AUTH XOAUTH2 command.

 (2)  Create a new source files <protocol>.[ch] where you should
 implement and a few lines to call them in other files.

  The commit to support POP3 in this repository will be a good
  example.

 (3)  decide the local port number where systemd listens and invokes
 xoauth2-pipe.

And last but not least, test, Test, TEST.

C MUA setting

Some MUAs may require another setting to completing the "mail routing
by the sender address".  For example, MH/nmh (yes I'm old fashioned)
has three delivery methods in their configuration and users choose one
of them.  The value sendmail/pipe doesn't speak SMTP but sends the
mail directly to MTA via pipe.  Because the correct sender address is
essential for the "mail routing by the sender address", MUA should
speak SMTP.  So MH/nmh users will need to set smtp or sendmail/smtp to
mts setting in order to cooperate with xoauth2-pipe.