[imp] Can't send mail after php upgrade

[Rick Emery]

By way of additional information:

The php-imap rpm is installed. Through my troubleshooting, I've discovered
that I am able to send mail using other clients (mozilla mail), so figure it
probably isn't an smtp/sendmail problem. I therefore assumed it must be a php
problem (since  the only change was upgrading the php rpms), so I fired up
SquirrelMail (which also uses smtp through localhost) and was able to send
messages (this one comes to you care of SquirrelMail). So, it wouldn't appear
to be specifically a php problem either.

Now, if I can just figure out what it is that horde uses to send email that
SquirrelMail doesn't...

Any ideas? Thanks in advance,
Rick