Notifications sent to AT&T via Comcast

provels

Hello. I have my FW setup to send notifications to Comcast.net and Outlook.com email addresses (working) and a cell (text) on Consumer Cellular, an AT&T MVNO (not working).
I'm sending to nnnnnnnnnn@txt.att.net.
Also tried nnnnnnnnnn@mms.att.net.
The emails are received almost immediately.

My delay/fail notifications include "Client did not present a certificate" and SMTP error 451.

I'm using smtp.comcast.net:465. Oddly my MS Outlook client uses 587, 465 does not work. And 587 doesn't work on the FW(?). Weird.
SSL/TLS is enabled.

Would anyone care to share their successful config? Thanks for reading.

Bob.Dig

@provels Kinda hard to understand what is actually happening. In general, Port 587 can use STARTTLS. Maybe this is mandatory in your case but unsupported.

provels

@Bob-Dig (if this helps)

Reporting-MTA: dns; resdmta-a2p-658371.sys.comcast.net [96.103.146.41]
Received-From-MTA: dns; resomta-a2p-647654.sys.comcast.net [96.103.145.231]
Arrival-Date: Mon, 17 Mar 2025 01:55:49 +0000

Final-recipient: rfc822; XXXXXXX@txt.att.net
Diagnostic-Code: smtp; 451 4.2.0 <XXXXXXX@comcast.net> server temporarily unavailable AUP#MXRT

Last-attempt-Date: Mon, 17 Mar 2025 16:29:53 +0000

Received: from resomta-a2p-647654.sys.comcast.net ([96.103.145.231])
	(using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 256/256 bits)
	(Client did not present a certificate)
	by resdmta-a2p-658371.sys.comcast.net with ESMTPS
	id tyJpt9Zn3SOV4tzhlt31AQ; Mon, 17 Mar 2025 01:55:49 +0000
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=comcast.net;
	s=20190202a; t=1742176549;
	bh=l198If4htI8LL1aGSFFlopPcb6CLX1VZlssoRNGC5/s=;
	h=Received:Received:Message-ID:From:To:Subject:Date:
	 Xfinity-Spam-Result;
	b=SCx6MaGtwj3Og6OC+cCBDQdw+o/Mzz/iwt3dduouLmvorSOO6k2BmcSklkRiroJbA
	 Yw+6Q0jU9dHr7IJNoNSDmeRJwoALRzCpZ0vuvsa+iZDWfH0D82NFdu2lqRTYVyoxId
	 XtrMb/eWyhPRUz3NxtMQ3TJWhHJ2S+wgdbQd/w0Ukqt8pub9FBG4jKtGQc52XHdA4T
	 q9TtJf1Hc8O1SRoXgTIrG1mJcTyj3bp6kWHISpUUmNgDGu7rlkTiGPBM++wNKroJSD
	 5Y1WeUAIOfXgvQ34NliA8dbWNlVxbEbUeCmD8QVp/od0Im0jRPcjDBAcJP+Vhjuaig
	 XcXHS2u9beJnQ==
Received: from fw.workgroup ([IPv6:<address>])
	(using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 256/256 bits)
	(Client did not present a certificate)
	by resomta-a2p-647654.sys.comcast.net with ESMTPSA
	id tzhktHB64A2cotzhltrhIc; Mon, 17 Mar 2025 01:55:49 +0000
Message-ID: <tzhktHB64A2cotzhltrhIc.1742176549.9c66cf2c9a1fe8fc519dd5f9c3415394.MISSINGID@comcast.net>
From: XXXXXXX@comcast.net
To: XXXXXXX@txt.att.net,XXXXXXX@comcast.net,XXXXXXX@outlook.com
Subject: fw.workgroup - Notification
Date: Sun, 16 Mar 2025 20:55:47 -0500
X-CMAE-Envelope: MS4xfKKoDygB6K/6w6yZxVRHPA1nOWMFMZgH9pIbhyERie14+9oIm8YJBG8mrbxLU/cAUEL9Q9TsbKLDmHfCyknJqHuQOG62Qlddt8yW5aEBlcnmykDEM4tF
 jlnOtmMxjDrQlpgqgvAMKtMf4PARI8nGSbuGKQYxOEPCsGrXtuqhwfgu5hzDPiLJRNOAeUsxtEAsG3o8fTIzXlRp9kzMs2/Jw600ulVCidLauo2Dneco+fun
 b6FGhphrIUPerGW4dIteYfRIchS2UmtVZsGjBQg4JleXm8ZDjcm02TSgQ6N4X57aAPxqsNpox0M4YlDzxZ86M30B9mV5zQh1bXf1YN9dR3g=

Bob.Dig

@provels said in Notifications sent to AT&T via Comcast:

"Client did not present a certificate"

This is normal and has nothing to do with any problem.

provels

@Bob-Dig Thanks for the reply. Subsequent error messages appear to show the SMS is being blocked as spam.
(AUP = Acceptable Use Policy, CNCT = Concurrent Connections, MXRT = Max Rate)

Final-recipient: rfc822; XXXXXXXXX@mms.att.net
Diagnostic-Code: smtp; 421 att-e2xms-ibgw-6001a.ext.cloudfilter.net cmsmtp 96.102.19.37 blocked AUP#CNCT

Final-recipient: rfc822; XXXXXXXXXX@txt.att.net
Diagnostic-Code: smtp; 451 4.2.0 <XXXXXXX@comcast.net> server temporarily unavailable AUP#MXRT

I likely have a ton of messages in queue and will wait for them to fail out and before testing again. Just leaving this for anyone who is having similar issues. Searches found many instances of this problem with other providers.
For example.:
Anyway, thanks again for the comments.