Universal Send Mail with Oauth2 for Consumer Sites

[rex64]

I can not figure out how to send mail with Oauth2 for consumer (home) Gmail, Yahoo, Outlook with a universal method... I saw Sendmail, but I do not know how to get the tokens easily and consistently. What is the easiest / best way? We currently are doing regular SMTP sending, but that will not be allowed after this month by Google. We want the end users to be able to type their email address and then it will pop up a webpage for them to sign into and give permissions to share token.

 

[Skydiver]

In the Microsoft documentation for the SmtpClient they are recommending MailKit.

SmtpClient Class (System.Net.Mail)

Allows applications to send email by using the Simple Mail Transfer Protocol (SMTP). The SmtpClient type is obsolete on some platforms and not recommended on others; for more information, see the Remarks section.

learn.microsoft.com