UnknownHostException seems odd.
From the stack trace, this looks like your code got the exception trying to connect to the mail server.
If the server were down, I would expect this. However, it would be some form of connection refused
error. This error is telling you that a dns lookup for smtp.emailsrvr.com failed. I'm assuming that is
the host you are configured to use and that it normally works.
If you are on a Windows machine, I'm no help. But if you were on Linux I would suggest looking
at /var/log/messages for dns problems. I was about to say look at your mail daemon logs because
you said the daemon crashed, but based on the host name you are connecting to, that is probably
on the email server on your provider.
If smtp.emailsrvr.com is not the email server you are configured to use, then where did that host name come from?
I'd add code to catch the exception, log it, sleep for a few seconds and retry a few more times (not infinitely) before bailing.
I'm sure I didn't say anything you don't already know, but I'm saying it just in case.