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AuthorForum: PowerTCP Mail for .NET
Topic: IMAP login fails with A2 NO AUTHENTICATE

From: USA
Posts: 14
Member Since: 05/04/16
posted February 2, 2017 8:26 AM

Hi, when trying to connect to a customer's Exchange server we are receiving the error "A2 NO AUTHENTICATE" when trying to connect, i.e. when calling IMAPObj.Authenticate()

We think this may be due to a certificate issue, but we are not sure. When the IMAPObj.Session.Security.ValidationCallback function is called, we always return "True" to allow any certificate.

We are trying to get more info on the Exchange environment, but wanted to start this thread in case the A2 NO AUTHENTICATE was a problem with a known solution. I believe our tech working with the customer has also tried the IMAP Sample app and it was having the same issue as our application.

I'll gather more info and report back.


Nick B (Admin)

From: Utica, NY USA
Posts: 614
Member Since: 05/25/10

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Custom Application Development

posted February 2, 2017 2:23 PM

Hello Mike,

There's no one solution for this; it suggests that the server is refusing the authentication mechanism attempted. It's possible that while the authentication mechanism (such as PLAIN) is advertised by your server, it is refused when used, like described here:

If you send in a log (such as from the IMAP Client sample - open the log window from the File menu before attempting to login) into support@dart.com, we can review it.

From: USA
Posts: 14
Member Since: 05/04/16
posted February 2, 2017 3:05 PM

Thanks Nick. I'll email support with the log and some additional environment info once I can discuss with a colleague here. I don't think he is back until Monday, so it could be a few days. Appreciate the quick response.
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