The event viewer repeatedly displays Warning 1088

Behaviour

The event viewer repeatedly shows the following message:

Subsequently, you will also find a SChannel error in the Windows applications event viewer:

Please note that the ID and the code may differ slightly.

Explanation

Windows 2008 R2 and later do not support older, weak cipher suites that are considered broken, either by default or after a Windows update. Therefore, no TLS connection is established if the submitting server is only capable of TLS. As a result, the warnings or errors mentioned above are logged.

The submitting server must then perform a fall back to plain text. To do this, it is necessary for the submitting server to establish a new connection, since the old connection, where no TLS connection could be established, must be closed.

The support of only obsolete cipher suites is definitely a problem of the sending server, if it does not do a fall back to plain text when no TLS connection is successfully established. The warnings in the log only indicate that the connections failed because the TLS handshake did not work; that is, no cipher suite could be agreed upon because no common one was found.

Some servers then simply use a cipher suite of their choice, which can then lead to further messages.

Should your communication be disturbed due to this behaviour, please contact the operator of the submitting server and point out the circumstances described here. It is then up to the operator to deactivate TLS or adapt his solution to the current state of technical development.