smtp2Shoutrrr

A simple SMTP server that forwards incoming emails to a Shoutrrr supported service.

Installing

First generate a new configuration file following this example:

# config.toml
# Port the SMTP server will listen on
Port = 11025

# Credentials for the SMTP server (required — the server refuses to start without them)
Username = "user"
Password = "nometokens"

# Configure recipients to forward emails to

# Multiple Targets (Recommended)
# Use the Targets array to send notifications to multiple services
[[Recipients]]
# Email addresses to forward emails from
Addresses = ["user@example.com"]
# Shoutrrr services to forward emails to
# See shoutrrr documentation: https://containrrr.dev/shoutrrr/
Targets = [
    "ntfy://ntfy.sh/my-ntfy-topic?tags=email",
    "discord://token@id",
    "slack://token@channel"
]

# Single Target (Deprecated)
# The Target field is still supported for backward compatibility
[[Recipients]]
Addresses = ["legacy@example.com"]
Target = "ntfy://ntfy.sh/legacy-topic?tags=thing"  # Will show deprecation warning

# Note: Repeat [[Recipients]] as needed

# Optional: Configure a catch-all recipient for unmatched email addresses
[CatchAll]
# Shoutrrr services to forward unmatched emails to
Targets = ["ntfy://ntfy.sh/catch-all-topic?tags=unmatched"]

The server refuses to start if the configuration cannot forward anything — no recipients and no catch-all, a recipient without addresses or usable targets, or a mistyped table name such as [[Recipient]], which TOML would otherwise accept silently. It also refuses to start without a Username and a Password: these used to fall back to username/password, which left the authentication gate open to the most obvious guess there is.

Clients must authenticate with the configured Username and Password before starting a mail transaction; an unauthenticated client is refused rather than relayed. A client that used to send without issuing AUTH has to be configured with the credentials above.

The reply the sending client gets reflects what happened to the notification: 250 once at least one target has accepted it, 451 when none did so the sender retries, and 550 for a message that cannot be parsed at all — a malformed Content-Type, for instance — which no retry could fix. A partial failure is logged but still accepted, since a retry would redeliver to every target and duplicate the notification on the ones that already have it.

From releases

• Grab the latest release from the releases page
• Put the configuration file in the same directory as the binary
• Run the binary for your appropriate platform

From source (development)

• Clone this repository
• Put the configuration file in the repository folder
• Run make quick-run

Using docker

• Create a config.toml file as described above
• Run the docker image mounting the Config.toml file as /config.toml and exposing the configured port:

docker run -v /path/to/config.toml:/config.toml \
    -p 11025:11025 \
    git.nakama.town/fmartingr/smtp2shoutrrr:latest

Development

Run the server with:

make quick-run

Send a test email with:

This will read the config.toml in the current directory to set the appropriate SMTP client configuration.

go run ./cmd/sendmail/.