[ic] Some emails can't be sent - could this be why ?

[DB]

As I said in a previous post, suddenly about one in three of my order 
emails don't get sent. The rest arrive normally. According to the 
catalog's error log:

/cgi-bin/STORE/process.html Unable to send mail using /usr/lib/sendmail

Could the fact that my transactions and ordeline tables have grown 
rather large (several hundred records) be the cause? Would more RAM help 
(1MHz PIII w/256MB RAM now). Or is my first theory about applying 
Redhat's recent glibc security path a more likely cause? Any clues at 
all are more than welcomed.

DB