Mailslurper connection timeout after 6 seconds

I'm trying to setup mailslurper for email testing but I keep getting a connection timeout after 6 seconds whether using telnet or netcat.

I have left the config as default and mailserver creates the database on startup.

connecting with telnet

$ telnet localhost 2500
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
220 Welcome to MailSlurper!
221 Bye
Connection closed by foreign host.

The mailslurper console gives this:

MailSlurper: INFO - 2016/03/11 22:24:06 libmailslurper: INFO - Worker 2 queued to handle connection from 127.0.0.1:41756
MailSlurper: INFO - 2016/03/11 22:24:06 libmailslurper: INFO - Reading data from client connection...
MailSlurper: INFO - 2016/03/11 22:24:12 libmailslurper: INFO - Connection timeout. Terminating client connection

I have also written a script to send an email but the mail is not saved or recorded in the log so not seen.