What is SMTP TLS Report

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Strengthening email security: TLS-RPT, STARTTLS, and MTA-STS protocols work together

As businesses become more reliant on email as a primary means of communication, the importance of hardening these channels against potential threats cannot be overstated. Transport Layer Security (TLS) ensures confidentiality and integrity of data transmitted across networks. There are several protocols that help encrypt the SMTP messaging channel, preventing cyber attackers from intercepting email communications. These include STARTTLS, DANE, and MTA-STS.

However, when using these protocols, your emails may not be delivered if the encryption attempt fails. TLS-RPT (described in) provides a feedback mechanism to report these delivery failures. We strongly recommend using TLS-RPT with the protocols. Let's take a look at how these protocols work together to strengthen email security. TLS-RPT (Transport Layer Security Reporting) is a standard for reporting email delivery issues when the email is not encrypted using TLS. Its importance in email authentication goes hand in hand with the reasons for enabling TLS encrypted email. TLS encryption technology ensures that every message sent to you is delivered securely. Many times, emails may not be delivered if the connection is not secure. With TLS-RPT, domain owners can monitor email delivery and connection failures.

Reports can include the following information so you can understand your email pipeline and address deliverability challenges faster. In SMTP email communications, TLS encryption is "opportunistic". This means that if an encrypted channel cannot be negotiated, the email will still be sent in an unencrypted (plain text) format. In fact, nearly 40 years ago, the SMTP buy bulk sms service email protocol did not support TLS encryption. This was later transformed in the form of the STARTTLS command. The STARTTLS command is only issued if both parties in the SMTP communication support TLS encryption. Otherwise, the email will still be sent in plain text. To get rid of opportunistic encryption in SMTP, MTA-STS () was introduced. The MTA-STS protocol ensures that the message is encrypted before it is sent. The email server or mail transfer agent (MTA) negotiates with the receiving server to see if it supports the STARTTLS command. If it does, the email is encrypted and delivered via TLS.

Otherwise, delivery fails. There are many reasons why TLS encryption can fail. In addition to both parties not supporting encryption, more nefarious reasons such as SMTP downgrade attacks can also cause TLS connections to fail. If MTA-STS is enabled, attackers cannot send information in plain text when a connection fails. But domain owners want to be aware of delivery failures. TLS Reporting (TLS-RPT) is a protocol that can notify you. In the event of a delivery failure, you will receive a TLS report in a JSON file format to the email address defined in your TLS-RPT record. Domain owners need to be kept informed of email delivery issues due to TLS encryption failures for emails sent from an MTA-STS-enabled domain. TLS Reporting makes this possible by providing this information. TLS-RPT Once a TXT record for TLS-RPT has been created and published on DNS, you can enable TLS reporting for a domain. This record must be published on a subdomain and you can create the record using our TLS-RPT Record Generator. Enter the email address where you want to receive SMTP TLS reports. You can contact your domain registrar to create a new TXT record for TLS-RPT. If you manage your DNS yourself, edit your DNS settings to include this record.