Patched version from jtlatuvm comment

2017-11-03

• Author: jtlatuvm from nagios plugin page (comment)
• check_smtp_send depends on Net::SMTP::TLS which is no longer maintained and breaks with new IO::Socket::SSL. That's when you'll see: invalid SSL_version specified
• The fix is to change check_smtp_send to use Net::SMTP which now directly supports STARTTLS.