[Mediawiki-l] New Password E-Mails Bounce, BUT Mod Notification E-Mails send successfullly

[Tonnis Wildeboer]

What is the difference between the way e-mails are sent for new passwords vs. the way they are sent for modification notifications?  The latter are being sent successfully while the former always bounce. Here is a line showing the bounce from the mail log:
 
....
Oct 13 14:35:16 ascari postfix/smtp[5305]: 8141C3BA035: to=<someone at mycompany.com>, relay=mycompany.com[74.220.207.117]:25, delay=1, delays=0.03/0/0.68/0.3, dsn=5.0.0, status=bounced (host mycompany.com[74.220.207..117] said: 550 Administrative prohibition (in reply to end of DATA command))
....

FYI, a simple php mail() command is successful, so that works too.
We are running MediaWiki 1.11.2-2 on Ubuntu 7.10.

Thanks in advance,

Tonnis