How to set Client using GSSAPI NTLM?

[ZinedineR]

I have SMTP service with authentication of GSSPI NTLM, is there anyway to achieve using this library? I noticed there is WithSMTPAuthCustom function, I wonder if I can use this

[wneessen]

Hi @ZinedineR,

we currently do not support GSSAPI for NTLM but you are right, WithSMTPAuthCustom() would be the way to do it in your local code. As long as your provided custom fuction, that implements the GSSAPI authentication for NTLM satisfies the smtp.Auth interface: https://pkg.go.dev/github.com/wneessen/go-mail@v0.4.1/smtp#Auth you should be able to work with it.

[ZinedineR]

so I have tried to copy ntlm.go from this library github.com/cmarkh/smtp, I have also changed so the Start(server *smtp.ServerInfo) to your smtp function. Here's the problem:

their library: func (c *Client) Auth(a Auth)

case 334:
			if msg64 == "NTLM supported" {
				msg = []byte(msg64)
			} else {
				msg, err = encoding.DecodeString(msg64)
			}

your library:

case 334:
				msg, err = encoding.DecodeString(msg64)
			

it seems because the return of msg64 is "NTLM supported", your smtp can decode the string properly. If you may have more free time, I would like to add NTLM auth to your library. I want to discuss more about this

[wneessen]

PRs are always welcome. When porting code from other libraries, though please make sure that their license allows it. Also please keep in mind that one of go-mail's principles is to only rely on the Go stdlib.

[ZinedineR]

Allright, thanks wneessen, I'll research more about it.