What is SMTP Error 602

Question asked by Brian A. - 1/8/2024 at 10:07 AM

Unanswered

I can't seem to find anything about what 602 is. I'm getting a bunch of these lately.

Delivery has failed to these recipients:

user@domain.con

Subject: Re: email subject

Remote Server returned: '602 Attempted to send the message to the following IPs:

xxx.xxx.xxx.xxx, xxx.xxx.xxx.xxx'

9 Replies

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Kyle Kerst Replied

1/8/2024 at 10:34 AM

Employee Post

The 602 error is a generic failure notice and you'll need to log on to SmarterMail as a system administrator, navigate to Manage>Troubleshooting>View Logs to search the Delivery log for this attempt in order to find the underlying error that prevented delivery.

Kyle Kerst IT Coordinator SmarterTools Inc. www.smartertools.com

rick Replied

1/9/2024 at 3:08 PM

Turning off "Enable TLS if supported by the remote server" located inside the domain's settings (under the Options card, Security) resolved this for me.

Not sure why.

Brian A. Replied

1/10/2024 at 2:11 PM

rick Replied
Yesterday at 5:08 PM
Mark As Answer
Turning off "Enable TLS if supported by the remote server" located inside the domain's settings (under the Options card, Security) resolved this for me.

Not sure why.

I think the issue is because the recipient's SSL Certificate is expired. The customer wants all TLS turned off for their domain because they don't want to deal with it. [Facepalm]

Kyle Kerst Replied

1/10/2024 at 3:59 PM

Employee Post

You should be able to turn TLS usage off on a per-domain basis in our latest release in the domain's settings on the Security card at least. Not to say its a good idea, but it IS doable :-P

Kyle Kerst IT Coordinator SmarterTools Inc. www.smartertools.com

Brian Bjerring-Jensen Replied

1/11/2024 at 1:53 AM

Getting shit load of these...

Error: 602 Failed to connect to the recipient's mail server. No MX records were found for the 'i-invest.se' domain. Status: 544 5.4.4 Host not found (not in DNS).Attempted to send the message to the following IPs: 77.111.240.13

Looking forward to seeing this resolved.

Steve Gaston Replied

4/4/2024 at 12:24 AM

Just seen this!

For me the message is

"Certificate ChainStatus has returned a non empty array."

-- EDIT --
The "solution" given above as per on a domain basis has worked

Matthew Titley Replied

7/24/2024 at 9:26 AM

Might be a coincidence but I'm seeing many more of these delivery failure reports after upgrading to 8930. For one customer I turned off the "Enable TLS" option in domain settings, reset retries on the "error 602" messages in the queue and they all went immediately. The delivery log did show the certificate mismatch. Looks like a wildcard cert issue of some sort. I've never encountered this prior to the recent upgrade so ST might want to look into it.

Matt

Zach Sylvester Replied

7/24/2024 at 9:32 AM

Employee Post

Hey Matthew,

I just opened a ticket for you to check if this is expected behavior or not.

Looking forward to hearing from you.

Kind Regards,

Zach Sylvester Software Developer SmarterTools Inc. www.smartertools.com

Tony Scholz Replied

7/24/2024 at 9:32 AM

Employee Post

@Matt,

IF you look in the Delivery log for the 602 error are you seeing a stack trace? I have seen this on some older servers that do not support some of the newer ciphers as well. Here is an example I found from an older server that was resolved by Moving (or upgrading ) the server to a newer OS.

[2024.07.23] 17:02:46.995 [46988399] RSP: 250-8BITMIME
[2024.07.23] 17:02:46.995 [46988399] RSP: 250-DSN
[2024.07.23] 17:02:46.995 [46988399] RSP: 250 CHUNKING
[2024.07.23] 17:02:46.995 [46988399] CMD: STARTTLS
[2024.07.23] 17:02:47.026 [46988399] RSP: 220 2.0.0 Ready to start TLS
[2024.07.23] 17:02:47.034 [46988399] Exception: One or more errors occurred. (Authentication failed because the remote party sent a TLS alert: 'HandshakeFailure'.)
[2024.07.23] Stack: at System.Threading.Tasks.Task.ThrowIfExceptional(Boolean includeTaskCanceledExceptions)
[2024.07.23] at System.Threading.Tasks.Task.Wait(Int32 millisecondsTimeout, CancellationToken cancellationToken)
[2024.07.23] at MailService.RelayServer.Clients.SMTP.ClientConnectionSync.InitiateSsl(Boolean validateAllCerts)
[2024.07.23] at MailService.RelayServer.Clients.SMTP.SmtpClientSession.GiveStartTls(String sessionId)
[2024.07.23] Inner Exception: Authentication failed because the remote party sent a TLS alert: 'HandshakeFailure'.
[2024.07.23] Inner Stack: at System.Net.Security.SslStream.ForceAuthenticationAsync[TIOAdapter](Boolean receiveFirst, Byte[] reAuthenticationData, CancellationToken cancellationToken)
[2024.07.23] 17:02:47.035 [46988399] Attempt to ip, '94.46.175.142' success: 'False'

Hope this helps.

~Tony

Tony Scholz System/Network Administrator SmarterTools Inc. www.smartertools.com

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