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Buck Hicks avatar Server

Using TLS1.0 or TLS1.1 to connect to Exchange Online with SMTP AUTH

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Buck Hicks

I have a Windows Server 2008 R2 that is being replaced in two months. Currently we use it for sending out reports, invoices etc. with SMTP Relay from multiple applications that are also being replaced at the same time the server is. My issues is that Microsoft has recently stopped allowing SMTP Relaying through Office365 with TLS1.0 or TLS1.1. Well not stopped because there is a work around. New opt-in endpoint available for SMTP AUTH clients still needing legacy TLS

I have followed all the steps (I think) correctly but still can't get it to work. The first thing I did is use PowerShell to Set-TransportConfig -AllowLegacyTLSClients $true and then set 4 email clients. I also went to my IIS 6 Management Console and changed the Smart host from smtp.office365.com to smtp-legacy.office365.com per the directions on this page. Next I logged into the Office365 Admin center and lastly I went to the three users that send out these emails and unchecked Authenticated SMTP From the Mange Email Apps tab.

And after doing all that I am still unable to send SMTP mail out from our system. The event log shows this error Message delivery to the host 'xx.xx.xx.xx' failed while delivering to the remote domain 'customer.com' for the following reason: The remote SMTP service rejected AUTH negotiation.

So just to be clear SMTP has been working all along and didn't not work until MS blocked them specifically so I don't think it is bad setting somewhere. Has anybody else run into this and know what step I missed or have any suggestions of what to try next?

By the way if it wasn't clear. This is just a temporary situation because were already planning on replacing this server. I just need to limp along for another couple of months.

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joeqwerty avatar
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joeqwerty
From the linked article: **Make sure that the mailbox is configured to allow sending using SMTP AUTH**.
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Buck Hicks avatar
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Buck Hicks
I read that the opposite. I unchecked the boxes for SMTP Auth. Anyway that was the issue. Thanks
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Buck Hicks avatar
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Buck Hicks
Why can't I mark this question resolved?
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vidarlo avatar
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vidarlo
Because it doesn't have a answer. You can self answer the question and mark that question as accepted.
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Buck Hicks avatar Server
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Buck Hicks

@joeqwerty answered the question in comments. The issue was that I had unchecked the SMTP Auth instead of leaving it checked.

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