Configure Transport Layer Security (TLS)

Resend supports TLS 1.2, TLS 1.1 and TLS 1.0 for TLS connections, but only requires TLS for sending when Enforced TLS is configured.

By default, Resend will attempt to make a secure connection, but will fall back to sending messages unencrypted when the receiving server does not support TLS. This is known as Opportunistic TLS.

You can instead configure Enforced TLS in the Resend Dashboard under the Configuration tab or with the Domains API or with a domains CLI command. This means that if the receiving server does not support TLS, your email will not be sent.

Learn more about Opportunistic TLS vs Enforced TLS.