Signald SMTP Bridge

Note: This is a pet project, just hacking for fun.

This is an SMTP server which bridges to Signal Messenger.

Emails can be sent to it with FROM: <SendingAccount>@signal.bridge and TO: <RecipientNumberOrGroupID>@signal.bridge. If you don't control the sending email address you can set SEND_FROM to specify the signal username that should be used when sending messages.

Plain text emails are sent normally via signal. HTML Emails are rendered using Headless Chrome and chromedp to a PDF and that PDF is attached to the signal message.

If you don't know what signald is yet best to stop and learn how that works first here: https://github.com/thefinn93/signald

Environment Variables for config

• SEND_FROM set to the signal username to send from when @signal.bridge email isn't used as the from address
• SEND_TO set to the signal username/number to send to when @signal.bridge isn't set in the recipient email address
• SMTP_USERNAME
• SMTP_PASSWORD
• SMTP_ALLOW_ANNON set to TRUE to enable anonymous access
• DEBUG set to TRUE to see full data of incoming mail in stdout

Deploying on Kubernetes

1. Open Deployment.yaml
2. Edit the /path/to/your/signald/config/folder value at the bottom of the file. This should point to the configuration directory of your signald. I got this onto the server by configuring signald locally then copying the data.

Note: This is a host mount so will work nicely on single node clusters, for multinode clusters a PVC or similar will be required.

1. kubectl apply -f ./Deployment.yaml

Getting started dev

Fill out .env-sample and copy to .env

Start headless chrome

docker run -d --network=host --rm --name headless-shell chromedp/headless-shell --remote-debugging-address=0.0.0.0 --remote-debugging-port=9222 --disable-gpu --headless

Start signald - assuming signalctrl already used to link account

make signald

Start the SMTP server

make run

Fire test emails

make test