tests: Corrected the SMTP tests to be RFC2821 compliant

The emails that are sent to the server during these tests were
incorrectly formatted as they contained one or more LF terminated lines
rather than being CRLF terminated as per Section 2.3.7 of RFC-2821.

This wasn't a problem for the test suite as the <stdin> data matched the
<upload> data but anyone using these tests as reference would be sending
incorrect data to a server.