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.net-coref#gmailemail-client

F# application Gmail auth issue

Update 2021.03.05: Seems like this doesn't happen with .net 4.8 (application or fsi) But always happen with .net 5.0 (application and fsi)

https://github.com/ingted/dotnet5mail

It is very weird that if I execute this code with .net4.8, the email would successfully be sent but not with .net 5.0. (It would say "Unhandled exception. System.AggregateException: One or more errors occurred. (The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.7.0 Authentication Required.")

  1. I already use the app password mentioned here Sign in with App Passwords
  2. I only use pure .net library

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Solution

  • System.Net.Mail.SmtpClient() is obsolete in .NET 5.

    SmtpClient has been obsolete since I believe .NET Core 2.0 and .NET 5 is more closely a progression of .NET Core 3.1, not a progression of .NET Framework 4.8.

    REF: https://learn.microsoft.com/en-us/dotnet/api/system.net.mail.smtpclient?view=net-5.0

    Microsoft recommends switching to MailKit.

    Nuget Link

    https://www.nuget.org/packages/MailKit/