is my server sending spam?

[jcmoon]

I noticed this line in my server's error logs (details slightly changed):

qmail-inject: fatal: unable to parse this line:
From: http://www.example.com/spammy-looking-path.html <[e-mail]>

I looked, and an error similar to this seems to appear a few times a day most days. Not every day, and some days more; on average about twice. It's actually two lines, not one, and it always appears in pairs. Sometimes the URL and email are repeated; usually they're not.

From looking about, it seems that when this error comes up, the message itself just disappears. But, are other messages getting out that I don't know about?

Has my server been compromised?

[edited by: engine at 11:22 am (utc) on Aug. 17, 2007]
[edit reason] examplified [/edit]