[imp] Can't send mail after php upgrade

[Rick Emery]

Following Brent's advice, I have upgraded php from arvin's 4.2.2 to 
horde's 4.2.3 (rpm -e the old ones, rpm -ivh the new ones). The upgrade 
went pretty painlessly, but now I can't send mail.

Using CVS HEAD of everything, I type my message in the compose window 
and, when I click send, the window refreshes with the message "unable to 
send data". The horde.log file has exactly the same message, and none of 
the other logs seem to indicate a problem (checked the mail and apache 
logs). I'm pretty sure my imap/smtp is working OK, since you're reading 
this message (same mail server, different client).

Anybody have any ideas?

Thanks in advance,
Rick