telegram-sendmail 1.1.0

A drop-in sendmail replacement that forwards system emails to Telegram.

telegram-sendmail

A drop-in sendmail replacement that forwards system emails to Telegram.

telegram-sendmail intercepts emails that system daemons — cron, logwatch, fail2ban, and others — send through the standard sendmail interface and forwards them to a Telegram chat as formatted messages. Any application that calls /usr/sbin/sendmail works without modification.

Two delivery modes:

• Pipe mode (default) — reads a raw RFC 2822 email from stdin, the standard interface used by cron and the majority of Unix system daemons.
• SMTP server mode (-bs) — runs a minimal SMTP state machine on stdin/stdout for applications that speak SMTP directly to sendmail.

Features

• Parses plain-text and HTML MIME emails; sanitises HTML through a two-pass pipeline before conversion to Telegram-compatible markup
• Detects MIME attachments without forwarding binary content
• Archives every raw email to a local spool file before Telegram delivery; no message is lost if the network is unavailable
• Smart message truncation at word boundaries with a configurable length limit
• Structured logging to syslog (LOG_MAIL facility) with an optional --console mode for interactive debugging
• Full sendmail-compatible flag support: -f, -r, -s, -bs, -t, -i, -oi, plus silent acceptance of positional recipient arguments
• Configurable HTTP retry strategy with exponential backoff
• EX_TEMPFAIL (exit code 75) on HTTP 429/5xx so MTA-aware daemons re-queue and retry automatically

Requirements

• Python 3.10 or later
• html2text ≥ 2024.2.26
• requests ≥ 2.31.0

Installation

Pre-built binaries for x86_64 and aarch64 with no runtime dependencies are attached to every GitHub Release. Installing from PyPI requires Python 3.10 or later:

# Recommended: install with pipx (automatic isolation)
pipx install telegram-sendmail

# Alternative: install into the system Python
pip install telegram-sendmail

Configuration

Create /etc/telegram-sendmail.ini (system-wide) or ~/.telegram-sendmail.ini (per-user):

[telegram]
token   = 123456789:AAxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
chat_id = -1001234567890

[options]
; All keys are optional — out-of-range values fall back to defaults.
;
; spool_dir             = /var/mail
; message_max_length    = 3800      (100–4096)
; smtp_timeout          = 30        (5–300)
; telegram_timeout      = 10        (5–60)
; max_retries           = 3         (0–10)
; backoff_factor        = 0.5       (0.0–10.0)
; disable_notification  = false

The config file contains the bot token. Permissions must be 0600; a WARNING is emitted to syslog on group- or world-readable files.

sudo chmod 600 /etc/telegram-sendmail.ini

A fully-annotated template covering every available key is available at telegram-sendmail.ini.example.

Registering as the system sendmail

telegram-sendmail does not register itself as /usr/sbin/sendmail automatically to avoid silently overwriting an existing MTA.

Simple symlink (no existing MTA):

TGSM_BIN=$(which telegram-sendmail)
sudo ln -sf "$TGSM_BIN" /usr/sbin/sendmail
sudo ln -sf "$TGSM_BIN" /usr/bin/sendmail

update-alternatives (Debian/Ubuntu, existing MTA present):

TGSM_BIN=$(which telegram-sendmail)
sudo update-alternatives --install /usr/sbin/sendmail sendmail "$TGSM_BIN" 50
sudo update-alternatives --config sendmail

Exit Codes

Code	Name	Meaning
0	EX_OK	Message delivered successfully to Telegram.
1	EX_ERROR	Operational failure: parse error, API error, or unexpected exception.
75	EX_TEMPFAIL	Transient failure (HTTP 429/5xx). Daemons will re-queue and retry.
78	EX_CONFIG	Configuration error: file missing, unreadable, or missing required key.

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For comprehensive setup instructions, configuration file templates, usage examples, and troubleshooting guides, refer to the full README on the telegram-sendmail GitHub repository.