msmtp wrapper which acts like sendmail and reads configs from envs. Useful in php docker containers to ensure that all mail() calls are working.

sendmail

#!/bin/bash
##
# This is custom wrapper for msmtp which acts like good old sendmail
# - It is used for php and cron
# - This is easier to configure for external mail server than sendmail
# - sendmail is just the default binary which other services will use
# - It needs following env: SMTP_HOST, SMTP_PASSWORD, SMTP_PORT, SMTP_AUTH, SMTP_USER
##

# This script gives itself as a parameter for msmtp
# to print out the password for --passwordeval option
# Check if msmtp called this script
if [ -n "$SMTP_PASSWORD" ]; then
    PARENT_COMMANDS="$(ps -o comm= $PPID)"
    if [[ $PARENT_COMMANDS =~ .*msmtp.* ]]; then
        echo $SMTP_PASSWORD
        exit 0
    fi
fi

# Deduce all used msmtp options from system ENVs
declare -a options

# Always extract recipients from message headers.
if ! [[ $* == *-t* ]]; then
    options+=('-t')
fi

# If user didn't provide from address with -f
# Use the SMTP_FROM variable or after that fallback for the --read-envelope-from
if ! [[ $* == *-f* ]]; then
    if [ -n "$SMTP_FROM" ]; then
        options+=("--from=$SMTP_FROM")
    else
        options+=('--read-envelope-from')
    fi
fi

# Use system tls chain
options+=("--tls-trust-file=/etc/ssl/certs/ca-certificates.crt")

if [ -n "$SMTP_HOST" ]; then
    options+=("--host=$SMTP_HOST")
else
    echo "[mail error] SMTP_HOST is not defined, mail can't be sent"
    exit 1
fi

# Log all mail requests
if [ -n "$SMTP_LOG" ]; then
    options+=("--logfile=$SMTP_LOG")
elif [ -f /var/log/mail.log ]; then
    options+=("--logfile=/var/log/mail.log")
fi

# Default port for smtp is 25 and it will work even without this option
if [ -n "$SMTP_PORT" ]; then
    options+=("--port=$SMTP_PORT")
fi

# Setup credentials
if [ -n "$SMTP_USER" ]; then
    options+=("--user=$SMTP_USER")
fi

# msmtp doesn't provide password option because usually it's unsafe
# Use recursive hack for passwordeval
if [ -n "$SMTP_PASSWORD" ]; then
    SCRIPT_PATH="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)/$(basename "${BASH_SOURCE[0]}")"
    options+=("--passwordeval=$SCRIPT_PATH")
fi


if [ -n "$SMTP_AUTH" ]; then
    options+=("--auth=$SMTP_AUTH")
elif [ -n "$SMTP_USER" ] || [ -n "$SMTP_PASSWORD" ]; then
    options+=("--auth=on")
fi

if [ -n "$SMTP_TLS" ]; then
    options+=("--tls=$SMTP_TLS")
fi

# Add our options and command line options for msmtp
msmtp ${options[@]} "$@"