Office 365 SMTP not working anymore with ASP.NET VB Page

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Office 365 SMTP not working anymore with ASP.NET VB Page

Jeff Thomas 21

I've attempted several changes that I received from Microsoft and still not successful. Everything worked until around February 2022. I understand that Microsoft made some changes in regards to SMTP authentication. I have the SMTP credentials setup in webconfig as seen below and the code is in VB. I appreciate any help I can receive!

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Answer 1

Lan Huang-MSFT 30,186 Microsoft External Staff

Hi @Jeff Thomas ,
I simply tested your code, you need to define username.text, vbCrLf will not report an error, or you can use the Environment.NewLine property instead.

Message.Body = "First Line" + Environment.NewLine + "second line"

My code below works fine, you can refer to it.

 <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>  
            <asp:Button ID="Button1" runat="server" Text="Button" />

<system.net>  
		<mailSettings>  
			<smtp>  
				<network host="smtp.office365.com" password="*****" port="587" userName="****" enableSsl="true"/>  
			</smtp>  
		</mailSettings>  
	 <defaultProxy>  
     <proxy usesystemdefault="False"/>  
   </defaultProxy>  
	</system.net>

Best regards,
Lan Huang

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Jeff Thomas 21 Reputation points

2022-11-30T16:39:22.597+00:00

Thank you for your response! My code was showing that "username" was not defined, but that was just from testing. It is defined and you can see that below now. I'm curious what kind of Office 365 Account you are using. I do have SMTP activated on the account I'm trying to use and it works via PowerShell, I just can't seem to get it working again through this page.
Lan Huang-MSFT 30,186 Reputation points Microsoft External Staff

2022-12-01T02:44:23.14+00:00

Hi @Jeff Thomas ,
Is there any error message?
You check that the username and password are correct.
Jeff Thomas 21 Reputation points

2022-12-01T02:49:08.46+00:00

The error message just says “failure to send email”. I see you are using an Outlook account. I have one one those, so I’ll try that and see if that will work.
Jeff Thomas 21 Reputation points

2022-12-01T13:07:06.307+00:00

This worked with my Outlook account, but I have no idea why it won't work with my Office 365 exchange account. I have a custom domain and I've checked all of the settings in Exchange and worked with both the Office 365 support and Azure support... Any thoughts on that? I could create an outlook account to use just for this, but need to find a way that I can mask the email address or come up with a "do not reply".

Thanks again for all your help!
Lan Huang-MSFT 30,186 Reputation points Microsoft External Staff

2022-12-02T03:32:34.207+00:00
Hi @Jeff Thomas ,
I think it is possible that your configuration is incorrect. Try putting enableSsl="false" and defaultCredentials="false" in the configuration.
Or you can refer to the code in this thread to see if there is any improvement.

mask the email address

You can use Regex to achieve this functionality.

Dim input As String = "******@abc.com" Dim pattern As String = "(?<=^[^@]+)[^@](?=[^@])|(?<=@[^.]+)[^.](?=[^.])" Dim result As String = Regex.Replace(input, pattern, Function(m) New String("*"c, m.Length)) //j**n@a*c.com

Best regards,
Lan Huang

Answer 2

Jeff Thomas 21

Thank you for your response! The thread you referenced had the fix! I need to add the "ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12" and it worked! See screen shot below.

I can't thank you enough!

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Office 365 SMTP not working anymore with ASP.NET VB Page

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