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106 lines
3.6 KiB
Markdown
106 lines
3.6 KiB
Markdown
# mailrelay
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`mailrelay` is a simple mail relay that can take unauthenticated SMTP emails (e.g. over port 25) and relay them to authenticated, TLS-enabled SMTP servers. Plus it's easy to configure.
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Prebuilt binaries are available [here](https://github.com/wiggin77/mailrelay/releases/latest) for Linux, MacOS, Windows, OpenBSD.
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## Use case
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Some older appliances such as scanners, multi-function printers, RAID cards or NAS boxes with monitoring, can only send email without any authentication or encryption over port 25. `mailrelay` can send those emails to your Gmail, Fastmail or other provider.
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Run `mailrelay` on a local PC or server and set your device (e.g. scanner) to send mail to it.
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`mailrelay` can be compiled for any Go supported platform including Linux, MacOS, Windows.
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## Encryption
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`mailrelay` uses TLS to connect to your SMTP provider. By default implicit TLS connections are assumed, meaning the connection is established
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using TLS at the socket level. This is in accordance with [RFC 8314 section 3](https://tools.ietf.org/html/rfc8314#section-3). These connections usually use port 465.
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However, some providers do not adhere to this recommendation (I'm looking at you Office365!) and only support the legacy STARTTLS command, which expects a non-encrypted socket connection at first, which is then upgraded to TLS. To enable this, set `smtp_starttls` to `true` in your config. You may also need to set `smtp_login_auth_type` to `true` which enables the legacy [LOGIN authentication](https://www.ietf.org/archive/id/draft-murchison-sasl-login-00.txt) method.
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These connections usually use port 587.
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## Testing your configuration
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You can send a test email using the `-test` flag. A email will be sent using the SMTP provider specified in your `mailrelay.json` configuration.
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```bash
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./mailrelay -config=./mailrelay.json -test -sender=dlauder@warpmail.net -rcpt=ender.wiggin@warpmail.net
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```
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## Example (Linux)
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On local PC (192.168.1.54) create file `/etc/mailrelay.json` with contents:
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/etc/mailrelay.json
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```json
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{
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"smtp_server": "smtp.fastmail.com",
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"smtp_port": 465,
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"smtp_starttls": false,
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"smtp_username": "username@fastmail.com",
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"smtp_password": "secretAppPassword",
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"smtp_max_email_size": 10485760,
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"smtp_login_auth_type": false,
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"local_listen_ip": "0.0.0.0",
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"local_listen_port": 2525,
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"allowed_hosts": ["*"],
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"timeout_secs": 30
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}
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```
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Run `mailrelay`,
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```Bash
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./mailrelay
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```
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Default location for configuration file is `/etc/mailrelay.json` but can be changed via `--config` flag. For example,
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```bash
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mailrelay --config=/home/myname/mailrelay.json
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```
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Configure your scanner or other device to send SMTP mail to server `192.168.1.54:2525`. Each email will be relayed to `smtp.fastmail.com` using the credentials above, including any file attachments.
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## Example 2 (Linux - Systemd service)
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Create configuration file as above, and also create,
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/etc/systemd/system/mailrelay.service
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```ini
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[Unit]
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Description=Mail Relay Service
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After=network.target
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StartLimitIntervalSec=0
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[Service]
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Type=simple
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Restart=always
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RestartSec=5
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ExecStart=/usr/local/bin/mailrelay
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[Install]
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WantedBy=multi-user.target
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```
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Copy `mailrelay` to `/usr/local/bin/`.
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Run,
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```Bash
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sudo systemctl start mailrelay
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sudo systemctl enable mailrelay
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```
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Now `mailrelay` runs as a service daemon and will automatically start after reboot.
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## Feedback
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Send any questions or comments to wiggin77@warpmail.net
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