said by hawkestar 
:Of course, the tech support is determined that the issue is on my end
NOTHING has changed within my system in the past 24 hours. And no, I will NOT re-install OE just to get them to help me.
I am using thunderbird for my client. Yesterday, I sent mail to this particular address just fine. Starting today, I get the following issue:
An error occurred while sending mail. The mail server responded:
[TEMPFAIL] destination not valid within DNS. Please verify that your email address is correct in your Mail preferences and try again
Now mind you, I can send to this person's other email address and I have no problems sending to anyone else. It is just her work address with this issue.
The issue is out of your hands. Your ISP mail server can't find the MX for the destination. It is listed as a temporary failure. If you have a different mail service, try using it. If MSN Hotmail or Yahoo! Web Mail work, your ISP has a DNS issue. If another server also fails, there are problems with the MX server at the destination.
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