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    Section 22.A.i: Users [of Optimum Online] may not run any type of server on
    the system. This includes but is not limited to FTP, IRC, SMTP, POP, HTTP,
    SOCKS, SQUID, DNS or any multi-user forums;

    Section 22.B.i: Users [of Optimum Online Boost and Optimum Online Ultra] may 
    not run any servers except for a webserver (HTTP) and mail (SMTP) on the 
    system.  This includes but is not limited to FTP, IRC, POP, SOCKS, SQUID, 
    DNS or any multi-user forums.

In my case, I was running an sftp server that worked for a while and then 
mysteriously stopped. When I contacted support, I was apprised of their policy, 
which I can only assume that they had reactively enforced.

-- 
- Bryan