sendmail leaves a lot of cores in the VDS
Check sendmail logs (var/log/maillog) to see if sendmail receives mail for users that are in VDS/etc/passwd but not on VDS/etc/features files.
for example, mail sent to: mail@VDS_DOMAIN
This is a list of such users: bin, daemon, adm, lp, sync, shutdown, halt, mail, news, uucp, operator, games, gopher, gdm, xfs
Add the user to VDS/etc/features file
the syntax is: :=,=
quota value can be:
-1 for disabled the service
0 for unlimited quota
or any absolut number for quota in MB.
Please note: script or cron are probably used to send these mails to those users.
You can also change the recipient address in the script to solve this problem.
This has been fixed for version 3.7 and is only relevant for 3.5
Please backup all files before modifying them