SMTP Server response to long e-mails

Guys,

I am making a VB.NET e-mail client using the TCPClient class. I am able to
connect to the server and retrieve messages that are within the size of the
SMTP server buffer. However, when the message is too long, the server sends
only part of it.

What should I do next to get the server to send the rest of the message? Is
there another command that tells the server to continue sending information,
or should I just read from the stream again (which will cause the TCPClient
to block until there is data) hoping that the server will send the rest of
the information automatically?

Thanks!