I've seen several trojans over the last year take advantage of destination TCP 53 because most people miss that little detail in their firewalls.
I don't believe in block all approaches anyway, but if you're going to walk down that path you may as well to the research to make perfect rules.
Most of those protocols listed are TCP only, excepting DNS, and SMTP doesn't do jack with port 26... so I don't know where that came from.
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