I have a VPS running CentOS 6. When the system tries to send daily newsletter, after some time (e.g. after sending about 2000 emails), I get error "Unable to send mail" and the system memory goes really high. Till this moment, the mails are delivered normally.
The rest symptoms are:
I cannot see anything on /var/log/maillog (File seems not to be written)
All files on /var/spool/mail have 0 bytes size.
From time to time on httpd log I get errors like: /usr/sbin/sendmail: error while loading shared libraries: libc.so.6: cannot open shared object file: Error 23
"Activate mail service on domain" setting in Plesk is deactivated.
Any idea on what's going wrong here?