Transport Layer Security Error #25 (WinSock): No information received from the server.

Problem Description

When sending email with AspEmail or AspEmail.NET under TLS, the following error occurs:

Transport Layer Security Error #25 (WinSock): No information received from the server.

Solution

In most cases this error indicates that the SMTP server requires TLS 1.2 or higher, while AspEmail attempts to communicate with it via TLS 1.0.

AspEmail and AspEmail.NET offer support for TLS 1.2 as of Version 5.5. If you are using an earlier version, please upgrade. If you are already using version 5.5+, make sure your script does not use specify the TLS version to be "1.0" via the property TLSVersion.

Also, some SMTP servers which require TLS 1.2 also require that the client application support RSA/SHA256-based signatures, and throw the above error otherwise. AspEmail and AspEmail.NET offer support for RSA/SHA256-based signatures as of Versions 5.6.0.1 and 5.6.0.5189, respectively.

The above error can also be caused by the lack of the "renegotiation info" extension in a TLS 1.2 handshake as some SMTP servers require it. As of AspEmail 5.6.0.5 and AspEmail.NET 5.6.0.5338, this extension is included in the handshake.