Hi , can you please share link of latest dll build on latest runtime .net framework of Mail.dll and Proxy.dll
You can find the latest versions of Mail.dll .NET email client in the download section: https://www.limilabs.com/mail/download
You can find .net framework (.net 2.0, .net 4.5, .net 4.8), .net standard, .net 5.0 and .net 6.0 versions in appropriate folders under Redistributables folder (either in the installation folder after installation -or- in the zip archive).
It is also available through nuget: https://www.nuget.org/packages/Mail.dll/