Hosted System emails stopped Feb 7th

Question

We have a 3rd party system hosted locally which sends appointment emails daily. These were showing failures on some over last few months but stopped completely on 7th February. An organisation in a different region using the same system also had the same email failure on 7th Feb. We use the following settings in our system to send via microsoft SMTP server on port 587

<add key="EmailServer" value="smtp.office365.com" />
<add key="EmailServerPort" value="587" />
<add key="EmailDefaultSender" value="REMOVED@Anonymous .scot" />
<add key="EmailServerUseSSL" value="Require" />
<add key="EmailServerUseCredentials" value="false" />
<add key="EmailServerUsername" value="REMOVED@grampian.nhs.scot" />
<add key="EmailServerPassword" value="REMOVED" />
<add key="EmailServerPasswordEncrypted" value="1" />

I can provide the email address if someone from microsoft can help check the account for being blocked?

The local system hasnt changed and the local eHealth team say the server the system hosted on isnt blocking emails being sent.

The typical error message we get is as below:

265 : The system has been unable to send the Email.

Date:
24/02/2022 12:34:15

User:
6dcaa497c4740314 (NHSG\lawric2)

Active Form:
Diary

Message:
Failure
sending mail.

Source:
System
EmailPreview

Stack Trace:
at System.Net.Mail.SmtpClient.Send(MailMessage message)
at Genohsis.ADM.Controller.EmailController.sendEmail(Boolean p_bSaveEmail,
String p_strEmailFileName, Boolean p_bFromPreview, Int32 p_iEmailIndex, String p_strReminderReportName, String p_strRecordOriginalStatus, SmtpClient objSmtpClient, Boolean p_bRunAtLogin)

Target Site:
Void Send(System.Net.Mail.MailMessage)

Session
Information:
SessionID: 1xycycklvzlwohzno4pcjvfp
System Entry: Start
Active Person: 85de68f48ad72c05

Record Status: New

Email Status Code:
GeneralFailure

Can anyone help with this? It is weird two different organisations had their emails cut using the same system on 7th Feb leads me to feel microsoft have changed spam settings maybe nationally? Any help appreciated.

Answer 1

Are you still using the TLS1.1 or 1.0?

https://techcommunity.microsoft.com/t5/exchange-team-blog/new-opt-in-endpoint-available-for-smtp-auth-clients-still/ba-p/2659652

That changed this month and is no longer allowed so the legacy auth endpoint is avail

Answer 2

Yea, you have two options:

Upgrade to TLS 1.2 if that is the issue

or:

To take advantage of this new endpoint, admins will have to:

Set the AllowLegacyTLSClients parameter on the Set-TransportConfig cmdlet to True.
Legacy clients and devices will need to be configured to submit using the new endpoint smtp-legacy.office365.com

So for you:
<add key="EmailServer" value="smtp-legacy.office365.com" />

and then ask the Exchange Admin for the tenant to allow:
Set the AllowLegacyTLSClients parameter on the Set-TransportConfig cmdlet to True.

They started rolling this out this month so it could have happened at any time.