The error occurs when an Outlook client tries to connect to a mail server using a non-supported encryption protocol.

Most often, this problem occurs if your mail server supports only TLS 1.2 and 1.3 protocols. For example, Windows 7 only supports the legacy TLS 1.0 and 1.1 protocols by default, which are no longer used by public mail servers. The Outlook client uses the WINHTTP transport to send or receive data over TLS. If TLS 1.2 is not supported or is disabled on the winhttp level, Outlook won’t be able to connect to a server due to an unsupported encryption type.

To fix this problem, you need to enable TLS 1.2 support in Windows 7. Windows 7 supports TLS 1.2, but it is not enabled by default (unlike newer OS versions – Windows 8, 10, and 11).

In order to enable TLS 1.2 on Windows 7:

1. Make sure that Windows 7 SP1 is installed;
2. Manually download and install the update KB3140245 from Microsoft Update Catalog.

Download and install MicrosoftEasyFix51044.msi patch

• Restart your computer.
• The patch mentioned above adds the following options to the registry:
• A DefaultSecureProtocols parameter with the value 0x00000a00 in HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\WinHttp.
• In a 64-bit Windows version, you have to create this setting under HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows\CurrentVersion\Internet Settings\WinHttp.
• The 0x0A0 parameter leaves SSL 3.0 and TLS 1.0 enabled for WinHTTP, and enables TLS 1.1 and TLS 1.2 as well. If you want to allow a client to use only TLS 1.1 or TLS 1.2, change the value to 0xA00.

• Create new subkeys TLS 1.2 and TLS 1.1 under HKLM\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\.
• Create a Client key in each registry section. Then open each Client key and create a DWORD parameter DisabledByDefault with the value 0x00000000.