I have seen how bugsense, sentry etc work. I like the way you can get the error/crash reports. What I want is a solution like those but for internal use. Using an external api like bugsense is out of the question.
Is there any similar open source solution that can be used internally?
On
If you are already logging properly, and are requiring a more granular configuration you could give logstash a try. It is basically a logshipper with various input, filter and output modules, including email as an output method.
The input can be configured to parse your existing logfiles, recieve messages from a queue and many more. For UDP/IP based logging, take a look at logstash-gelf which is basically an adapter for automated generation of well formed logging meta data. If you plan on parsing your Logfiles, look out for the "multiline codec" in regards to parsing stacktraces and "grok" as a filter for parsing the log entries. For grok, I found that the Grok debugger is a big help.
E.G.: Once you have your logs routed through the input, and your logging is configured to use a named logger for the emailed messages you can tag them in logstash input and tell the output to send an email if a message with the tag is coming through.
I think using a specific logger (slf4j, log4j...) could be used. It can send e-mail for example for FATAL log with stack trace and what you want.