Forgejo can be set to send emails such as a registration confirmation, either with [Sendmail](https://man7.org/linux/man-pages/man8/sendmail.8.html) (or compatible MTAs like Postfix and msmtp) or by connecting to an SMTP server.
Directly use SMTP server as relay. This option is useful if you don't want to set up MTA on your instance but you have an account at an email provider.
> **NOTE:** authentication is only supported when the SMTP server communication is encrypted with TLS or `HOST=localhost`. This is due to protections imposed by the Go internal libraries against STRIPTLS attacks. TLS encryption can be through:
- STARTTLS (also known as Opportunistic TLS) via port 587. Initial connection is done over cleartext, but then be upgraded over TLS if the server supports it.
- SMTPS connection (SMTP over TLS) via the default port 465. Connection to the server use TLS from the beginning.
Both `SMTPS` and `STARTTLS` combined with `IS_TLS_ENABLED=true` are known as Implicit TLS and is recommended by [RFC8314](https://tools.ietf.org/html/rfc8314#section-3) since 2018.
> **NOTE:** For Internet-facing sites consult the documentation of your MTA for instructions to send emails over TLS. Also set up SPF, DMARC, and DKIM DNS records to make emails sent be accepted as legitimate by various email providers.
