Email error question

Hey. I recently got this error whilst sending email to a friend of mine.

I get this error from only one of my email addresses, and only when sending to the guy. I can send from my problem account address to other addresses, and I appear to be able to send from other addesses to their problem account.

Can anyone tell me if:
a) This error is on my side or their side;
b) If this error is consistent with blacklisting (don't ask... it's complicated).

 

tm: Is that a guess, or is the error message actually consistent?

Halo: I don't think so. How can I check?

The client I'm using is php Horde. So it's on the web host providers's web server. I should think it would be correctly configured, yes?

 

Error 550 is an authentication error.

When I used to work for an ISP, we would see this when people would use our SMTP server and connect through a different ISP. Or, visa versa. The reason it happens is because 99% of the SMTP servers out there authenticate by you being on the same network, not by user/pass.

Seeing how you can't really being doing that, then I would go to the next reason we saw these errors.

Some mail server software (on the recipient end) freaks out if the email headers in your email is not correct (which is by no means anything you have control over).

The other time we saw this was when the recipients mail server was down.


And lastly, yes, we saw this when a recipient or sender was blacklisted.

 

Turns out the mail server was down, and the second account I tried was just throwing the error messages away. To Yahoo: Gee, thanks guys.

To MG: Thanks guys!