Problem with Sent Emails

You must have detailed error in the log file.
If message does not help you to fix issue, please report it here.

When you have such a message "contact your administrator", it means you have some error reported in the log file. Please report error message here.

For information, this "not very explicit" message is "normal". It is a security way to hide information to some hacked that would try to discover ways to hack system from error messages.
If your environment is "secure" (local network for instance) or just to try for a short period, you can set debugLevel to 3 (debug). In this mode, the error message is directly displayed on screen...

Get the log file.
By default it is in /files/logs/projetor_yyyymmdd.log
Search for an error.
Post it here.