550 Unrouteable address error

Hello Experts,

I am having problems with emails sent from my server using the php mail() function.  I get the following error in my maillog:

Sep 27 01:50:15 xx-xx-xx-xx postfix/smtp[15523]: E04AB1380532: to=<joe@othersite.com>, relay=mail.othersite.com[xx.xx.xx.xx]:25, delay=16, delays=0.11/0.01/16/0.1, dsn=5.0.0, status=bounced (host mail.othersite.com[xx.xx.xx.xx] said: 550-Verification failed for <xxx@localhost.localdomain> 550-Unrouteable address 550 Sender verify failed (in reply to RCPT TO command))

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Anyone know how to resolve this?

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OmniUnlimitedAuthor Commented:
Ok, so how do I provide valid credentials?  I am the owner/user of my domain, and no, I am not interested in using a third party email service like Gmail.
OmniUnlimitedAuthor Commented:
Sorry takecoffe, I found the answer here:


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OmniUnlimitedAuthor Commented:
Suggestion provided did not produce a solution to the problem.
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