WordPress mail function not working correctly

– WordPress appending “d” to email addresses

My hosting is at WiredTree, and of all my WordPress sites (10-15), all send out emails correctly with the default email settings. For my main install however, it isn’t working, either with built-in notification emails or with external contact form plugins. After going through my mail logs, I noticed (see below) that for some unknown reason, a ‘d’ is being added to the end of every email address, resulting in all emails being invalid.

I have reuploaded a fresh copy of WordPress files and all the plugins, to no avail. I’m wondering if it is something filtering the default mail class or something, but I don’t know how to track that. Any ideas how I should go about tracking down the error? I’ve looked everywhere that I can and am coming up empty.
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2011-11-29 03:03:50 1RVJbR-0000Pe-Tu <= [email protected] U=sreviews P=local S=1219 [email protected] T=”Re: Submitted form (copy)” 2011-11-29 03:03:50 1RVJbR-0000Pe-Tu ** stxxx@wiredtree*.comd* R=fail_remote_domains: The mail server could not deliver mail to stxxx@wiredtree*.comd*. The account or domain may not exist, they may be blacklisted, or missing the proper dns entries. 2011-11-29 03:03:50 1RVJbR-0000Pe-Tu Completed

Look at [email protected]. Now I verified I typed in the right address. Here is another example:

2011-11-29 02:01:57 1RVIdZ-0008O0-3h <= [email protected] U=sreviews P=local S=1190 [email protected] T=”Re: Submitted form (copy)” 2011-11-29 02:01:57 1RVIdZ-0008O0-3h ** dexxx@derekperkins*.comd* R=fail_remote_domains: The mail server could not deliver mail to dexxx@derekperkins*.comd*. The account or domain may not exist, they may be blacklisted, or missing the proper dns entries. 2011-11-29 02:01:57 1RVIdZ-0008O0-3h Completed

For some reason the page appends a “d” at the end of the email.