Did you mean manually quarantine an email? If that is what you meant than I wonder why would anyone quarantine email manually. I would be happy to learn if there is any technicality associated with it.
James, Sophos has an add-in for Outlook that does SPX. I bet it would be straightforward to have one that added a sender to your personal blacklist. You might make a suggestion or vote for an existing one at http://feature.astaro.com.
In fact, a properly-tuned SMTP Proxy should need very few blacklisted addresses.
One of the biggest problems I see is folks signing up for mailing lists, sometimes inadvertently. These bulk emails are not spam and blacklisting the sender is often ineffective. Virtually ALL of these emails have an opt-out at the bottom of the mail. Sometimes there are two, one for a particular client and one for the bulk mailer's complete list. The next time someone complains about the amount of spam they're receiving, ask them to forward a few samples.
