Exchange 2019 Relay connector START TLS issue
Max Coder
I have been using Exchange Server 2019. We are using wildcard certificate. I am trying to use the MailKit package which seems to be the recommended way to send email from PowerShell.
But I am getting an error message like below.
System.NotSupportedException: The SMTP server does not support the STARTTLS extension.
Commands I use for the relay connector:
New-ReceiveConnector -Server "EX01-2016" -Name "SMTP relay" -TransportRole FrontendTransport -Custom -Bindings 0.0.0.0:587 -RemoteIpRanges 192.168.1.60
Set-ReceiveConnector "EX01-2016\SMTP relay" -PermissionGroups AnonymousUsers
Get-ReceiveConnector "EX01-2016\SMTP relay" | Add-ADPermission -User "NT AUTHORITY\ANONYMOUS LOGON" -ExtendedRights "Ms-Exch-SMTP-Accept-Any-Recipient"
Set-ReceiveConnector "EX01-2016\SMTP Relay" -AuthMechanism ExternalAuthoritative -PermissionGroups ExchangeServers
$TLSCert = Get-ExchangeCertificate -Thumbprint "XXXXXXXXXXXXXXXXXXXXXXXXXXXXX"
$TLSCertName = "<I>$($TLSCert.Issuer)<S>$($TLSCert.Subject)"
$tlscertificatename = "<i>$($cert.Issuer)<s>$($cert.Subject)"
Set-ReceiveConnector "EX01-2016\SMTP Relay" -TlsCertificateName $TLSCertName
FQDN under scoping : relay.domain.com
Philip Elder
If you have an Exchange Server on-premises why?
https://blog.mpecsinc.ca/2018/06/exchange-2013-set-up-receive-connector.html
We set up a dedicated relay for internal services to use.
Philip Elder MCTS
Senior Technical Architect
Microsoft High Availability MVP
MPECS Inc.
E-mail: Phili...@mpecsinc.ca
Phone: +1 (780) 458-2028
Web: www.mpecsinc.com
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Michael B. Smith
Who told you to use mailkit?
If you are all on-prem, I’d still be using send-mailmessage. If you are hybrid, I’d be using Send-MgUserMail.
From: ntexc...@googlegroups.com <ntexc...@googlegroups.com>
On Behalf Of Max Coder
Sent: Thursday, June 26, 2025 4:04 PM
To: ntexchange <ntexc...@googlegroups.com>
Subject: [ntexchange] Exchange 2019 Relay connector START TLS issue
Hi,
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