after ftp. ftp.umass.edu, I get "UNKNOWN HOST" There is no prompt for username. What do I do so that I can ftp files out? Or even email, to an unknown host.

i think you are typeing it incorrectly.

i get a dns response from that host.
Non-authoritative answer:
Name: isis.oit.umass.edu
Address: 128.119.166.99
Aliases: ftp.umass.edu

type "ftp ftp.umass.edu" then it should prompt you for a u/p

If you are getting Unknown Host, This either means that
1. Host name that you have provided is Invalid.
2. DNS is not configured.
3. There might be some problem in the network
4. or the Host which you want to access is down.

Try to Ping the host.

And by looking the command that you have provided "ftp. ftp.umass.edu", here there is a problem - ftp followed by dot(.), but this will not give UNKNOWN HOST; indeed it will give "Command not found". So I assume that you are issuing the command correctly.

And to know whether you can mail on that server:
If you network programming, you can then write a DNS query to look for MX record, and if such record exist, then you can mail to that server also.