sendgmail

sendgmail is a tool that enables git send-email to send patches from a Gmail account without using SMTP.

This tool has been modified from its original version. This new version, inspired by siketyan/sendgmail, uses the Gmail users.messages.send API to send the email instead of using SMTP. This has the following advantages:

• The scope of the OAuth token can be limited to only sending emails.

This avoids the potential danger created by generating a token with full Gmail permissions, which is necessary to send emails through Gmail using SMTP (when not using an app password, which grants even more permissions).

• Sent emails will always appear in the "Sent" folder in Gmail regardless of whether or not you CC yourself.

In contrast, when a message is sent via SMTP, the message will not appear in the "Sent" folder unless you CC yourself.

[!CAUTION]
Unfortunately, it seems that sending patches via the Gmail API has some of the same limitations as sending via the Web UI.
Namely, that some patches will get mangled by Gmail's insistence on line-wrapping certain long lines in plaintext emails.
To avoid sending corrupted patches to public mailing lists, sendgmail automatically detects patches that are likely to be mangled by Gmail and will refuse to send them.

Getting Started

Step 1: Install sendgmail

go install github.com/cyrozap/sendgmail@latest

This will install sendgmail to $GOPATH/bin/sendgmail.

Step 2: Create Google OAuth2 Client and Credentials

• Create a Google Cloud project

• Visit the Google Cloud console.

• Open the project picker (to the right of the Google Cloud logo, or press Ctrl+O).

• Create a new project (name it e.g. sendgmail).

• In the Notifications window, wait for the project to finish being created, then click Select Project when the button appears.

• Enable the Gmail API

• Click this link to begin the process to enable the Gmail API for your sendgmail project.

• Click Next, then click Enable.

• Create the OAuth configuration

• Open Navigation menu (≡) > APIs & Services > OAuth consent screen.

• Under where it says "Google Auth Platform not configured yet", click Get started.

• Set the App name to sendgmail.

• Set the User support email to your own email.

• Click Next.

• Set Audience to External, then click Next.

• Set the Contact Information email address to your own email, then click Next.

• Read and agree to the Google API Services: User Data Policy, then click Continue and then Create.

• Create the OAuth client and download credentials

• Click Create OAuth client.

• Set Application type to Web application

• Set the Name to sendgmail, or leave it as-is.

• Under Authorized redirect URIs, click Add URI.

• If you're using sendgmail -setup on the same computer that your browser is logged in to, set the URI to http://localhost:8080/oauth2callback.

• This will configure sendgmail -setup to listen on that port for your browser to send it the authorization code.

• You can change the port to another number if sendgmail -setup is not able to listen on port 8080 on your computer.

• You can also set a loopback IP (like 127.0.0.1 or [::1]) as the host instead of localhost, if you prefer.

• If you need to run sendgmail -setup on a different computer from the one that your browser is on, set the URI to https://google.github.io/gmail-oauth2-tools/html/oauth2.dance.html.

• This will cause the authorization code to be displayed in your browser, and from there you'll have to copy and paste or manually enter the code into sendgmail -setup.

• Click Create.

• In the window that appears, click Download JSON to download the OAuth client credentials.

• Move the credentials JSON into the sendgmail configuration directory:

CONFIG_DIR="${XDG_CONFIG_HOME:-${HOME}/.config}/sendgmail"
      mkdir -p "$CONFIG_DIR"
      chmod 700 "$CONFIG_DIR"

      # Move the credentials file (must be named "config.json")
      mv path/to/credentials.json "$CONFIG_DIR"/config.json
      chmod 600 "$CONFIG_DIR"/config.json

• Enable the gmail.send API scope

• Click Data Access, then click Add or remove scopes.

• Where it says Enter property name or value, type gmail.send and press the Enter/Return key.

• Check the checkbox just to the left of where it says "Gmail API" in the single row that should be visible.

• Click Update, then click Save.

• Add yourself as a test user

• Click Audience.

• Under Test users, click Add users.

• Enter your own email, then click Save.

Step 3: Generate OAuth2 Token

Run the following command to perform the OAuth2 authorization:

# Replace with your Gmail address
$GOPATH/bin/sendgmail -sender=USERNAME@gmail.com -setup

Follow the remaining steps in your browser. If you set the Authorized redirect URI to a local URL, then at the end of the process the token will automatically be sent to sendgmail. If you instead set it to .../oauth2.dance.html, then you'll have to copy the code and paste it where prompted by sendgmail.

Usage with Git

[!NOTE]
This assumes you've completed the OAuth2 setup.

Add the following section to .gitconfig in your home directory:

[sendemail]
    smtpServer = /full/path/to/sendgmail  # From $GOPATH/bin/sendgmail or custom path
    smtpServerOption = -sender=USERNAME@gmail.com