Support for NTLM

[RobinMeis]

Adding support for NTLM

[RobinMeis]

Docs: https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-smtpntlm/a048c79f-7597-401b-bcb4-521d682de765

[RobinMeis]

Actually more complicated than it seemed when checking Microsoft's example. Due to negotiation flags there are couple of options that have to be supported. Skipping NTLM support for now