Created Issue: EHLO command not returning correct responses? [8630]

I downloaded the source code of smtp4dev 2.0.9 and playing around with the Rnwood.SmtpServer to see if I can embed it in a custom server. In my server, I register only the Rnwood.SmtpServer.Extensions.SizeExtension. When I send a message using Mozilla Thunderbird, the transaction fails and Thunderbird says that the server responds with just "SIZE". In my case, server ends up in an infinite loop.

So, I debug using a telnet session to the server:

```
Trying 127.0.0.1...
Connected to goten.local.
Escape character is '^]'.
220 (none) smtp4dev ready
EHLO example.com
250 Nice to meet you.
SIZE
```

This is where I notice that the server responded incorrectly, so I sent the QUIT command back to the server and the everything closed correctly.

```
QUIT
221 See you later aligator
Connection closed by foreign host.

```

If I am interpreting [RFC 1869](http://tools.ietf.org/html/rfc1869) correctly, I think each line of the EHLO response is suppose start with a "250" code:

```
ehlo-ok-rsp ::= "250" domain [ SP greeting ] CR LF
/ ( "250-" domain [ SP greeting ] CR LF
*( "250-" ehlo-line CR LF )
"250" SP ehlo-line CR LF )
```

I think this is a bug. Any thoughts?

Thanks,
Ralph