In WEBppliance Basic 3.5.10 when mail is delivered on the first attempt it will failed to be delivered and you will see an error message like:
Jun 18 14:39:39 server virthostmail: Chrooting to /home/virtual/site1/fst
Jun 18 14:39:39 server sendmail: h5IIddO31692: smtpquit: mailer virthostmail exited with exit value 127
This happens because WEBppliance Basic 3.5.10 has bandwidth turned off by default and what happens is virthostmail tries to load libensimvwhbw.so and because it is not there (because bandwidth is disabled for the site) mail will not be delivered on the first attempt. When this fails, the mail message is left in the mqueue directory, and when sendmail re-attempts to deliver the message it will succeed. To fix this problem run the following commands as root:
for c in site*; do ln FILESYSTEMTEMPLATE/bandwidth/lib/libensimvwhbw.so $c/fst/lib/libensimvwhbw.so; done
For any new sites that you add you can create a virtDomain.sh file in /etc/appliance/customization with:
ln /home/virtual/FILESYSTEMTEMPLATE/bandwidth/lib/libensimvwhbw.so lib/libensimvwhbw.so
This will hardlink the library into the virtual domain. This will be fixed in an upcoming version of WEBppliance.