Hi, Essentially, Dynamics 365 has full compatibility with TLS 1.2 only or v9. https://www.microsoft.com/en-us/download/details.aspx?id=57079 https://cloudblogs.microsoft.com/dynamics365/bdm/2017/09/28/updates-coming-to-dynamics-365-customer-engagement-connection-security/?source=crm TLS is not controlled by the E-mail router but of the security settings on the machine through the registry entries that would be used similar to a server that .Net would leverage. If you have TLS 1.2 enabled, TLS 1.1 and TLS 1.0 disabled for client on the server, and the SystemDefaultTLS registry keys configured – then the outgoing communication for .Net will be TLS 1.2. You can use the following registry key to enforce the TLS 1.2 rather than other versions. [HKEY_LOCAL_MACHINESOFTWAREMicrosoft.NETFrameworkv2.0.50727] “SchUseStrongCrypto”=dword:00000001 [HKEY_LOCAL_MACHINESOFTWAREWow6432NodeMicrosoft.NETFrameworkv2.0.50727] “SchUseStrongCrypto”=dword:00000001 [HKEY_LOCAL_MACHINESOFTWAREMicrosoft.NETFrameworkv4.0.30319] “SchUseStrongCrypto”=dword:00000001 [HKEY_LOCAL_MACHINESOFTWAREWow6432NodeMicrosoft.NETFrameworkv4.0.30319] “SchUseStrongCrypto”=dword:00000001 Supporting link – (+) CRM 2013 emails not being generated with TLS 1.2 protocol – Microsoft Dynamics CRM Forum Community Forum Hope this Helps! Regards, Venkatesh N