Error "535 Invalid Username or Password" when using as smtp relay

Discussion regarding the Standard version.
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Dieter
Posts: 4
Joined: Tue Feb 15, 2022 11:24 am

Error "535 Invalid Username or Password" when using as smtp relay

Post by Dieter »

We are using Mailenable Standard as SMTP relay server. Upgraded from 8.55 to 10.37

Since the upgrade some mails are not passing through anymore. When the concerned server connects we get the error "535 Invalid Username or Password". Before the upgrade this logging didn't appear.

EHLO EHLO server.domain 250-domain [ip-address], this server offers 4 extensions 223 38
AUTH AUTH LOGIN 334 ABCD 18 12
AUTH {blank} 334 EFGH 18 30 RTYU
AUTH JoLHJYTFIKJLMJ 535 Invalid Username or Password 34 62 RTYU

The server is configured SMTP-properties / Inbound / SMTP Port with "Requires connections to authenticate before sending email " NOT selected. So as far as I see there should be no check on authentication. In the relay-tab, "allow relay for authenticated senders" is NOT selected.

In https://www.mailenable.com/kb/content/article.asp?ID=ME020032 I don't see the error code 535

Any idea why incoming emails are not accepted with an "Invalid Username or Password" error while server is configured not having the need for authentication?

MailEnable-Ian
Site Admin
Posts: 9738
Joined: Mon Mar 22, 2004 4:44 am
Location: Melbourne, Victoria, Australia

Re: Error "535 Invalid Username or Password" when using as smtp relay

Post by MailEnable-Ian »

Hi,

The inbound connection from the remote mails server is issuing the AUTH command to the SMTP Service and trying to authenticate. Inspect the SMTP debug log in respect to the same socket number for more detail. There has been no changes that in the latest version that would cause this behavior.
Regards,

Ian Margarone
MailEnable Support

Dieter
Posts: 4
Joined: Tue Feb 15, 2022 11:24 am

Re: Error "535 Invalid Username or Password" when using as smtp relay

Post by Dieter »

Hi Ian,

Thanks for your reply. In the debug log I indeed find logging for the same events, also mentioning the invalid username/password.

ME-I0135: Authenticating User:username using Authentication Provider Credentials failed (unknown user or invalid password)
ME-I0070: (recv) socket [1476] was gracefully closed during [AUTH] command by the remote client ip-address.

I understand that in the latest version there can be no changes causing the difference. Unfortunately we have been running too long on version 8. 55 (about six years I realize now) and possibly in this long period some changes will have had impact. Just found the older release notes and had a look to it. Over the years I see a few times "FIX: Improved the audit logging of failed SMTP authentication attempts...", so I presume these can have some impact.

So basically I understand from now on, if you configure "no authentication" it must be "no authentication". Trying an authentication when "no authentication" is defined will cause a failure and no delivery. I'm hunting for my senders to change their configurations and remove the authentication.

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