Problem with authentication?

[black zero]

I am sending to gmail and yahoo as well as many other domains just fine. But this one domain (masked as XXXXXX.XX.XX) keeps rejecting my message. The error message is as follows:

Your message did not reach some or all of the intended recipients.

Sent: Tue, 11 Nov 2008 12:22:42 +0700
Subject: RE: XXXXXXX

The following recipient(s) could not be reached:

abc@XXXXXX.XX.XX
Error Type: SMTP
Remote server (XXX.148.6.XX) issued an error.
hMailServer sent: RCPT TO:<abc@XXXXXX.XX.XX>
Remote server replied: 550 Authentication turned on in your email client.

hMailServer

Any clue how to fix this on my side?

And oh, I am relaying email through my ISP's SMTP server, but have never had a problem like this with big email providers (gmail yahoo etc). I've checked spamhaus and didn't find my IP listed there, FYI.

[mattg]

That's a bad error message - doesn't really give much away does it?

Try contacting the recipients Mail server techs, and see if they can tell you more...

[black zero]

Will do.

Just want to confirm something,

Did this problem come from my side? I sincerely think no, it didn't come from my side....

Overall, thanks for your kind response.

[mattg]

I don't think it came from your side.

The logs will tell you exactly where the message came from. if you had logging enabled.