A long time ago, someone put forth the plausible-sounding notion that the use of certain words in e-mail will trip all kinds of spam alarms at the recipients’ ISP and get mail blocked. That might have been true for a few weeks in 1996, but it certainly isn’t now; ISPs today rely far more on sender reputation when they make delivery decisions. Nonetheless, there still seems to be a significant amount of superstition regarding content filtering.

I have a friend whom I’ll call Christine (since that’s her name). She’s a brilliant, energetic, one-person social media consulting firm, and she sends terrific mail – pithy, engaging, with great voice and compelling offers. But she insists on misspelling (or “munging”) the word “free” in her creative to put the spin move on content filters. “F.R.E.E. 5-Part E-Course”, “Fr*ee Teleseminar”, and “a half-hour of F-RE-E consulting” were all on offer in her last send. I tried to talk her out of mangling her creative a few months ago, but like some some habits, superstitions die hard.

That’s not to say that ISPs don’t perform some types of content filtering – they do, but not in the way Christine and others think. ISPs look at links in the body of the e-mail to catch two species of spam in particular: “phishers”, who are trying to collect log-in credentials for, say, on-line banking or social media accounts; and spam that sends clicks through to web sites that will surreptitiously load a worm, a virus, or other malware onto the computers of unsuspecting visitors.

Many ISPs and private inbound mail servers use a content filtering package called Spam Assassin. Spam Assassin assigns a cumulative score to the content of an e-mail message based on a wide range of criteria, all of which are highly configurable by the servers’ owners. If the score crosses a threshold – which is also configurable by the owner – the message might be rejected as spam based on content. But since the score is cumulative and weighted, the presence or absence of any single word – like “Free!” – is not sufficient to block mail.

Besides, free samples and trials are perfectly legitimate marketing tools used by the biggest companies in the world, every day. Customers enjoy receiving them, and respond positively to them. ISPs risk blocking legitimate, permissioned mail by blocking on words like “free” – so they just don’t do it. There are plenty of other, far more accurate ways of finding and blocking spam.

The take-away: senders with good reputation shouldn’t feel hampered by content filters when assembling their creative. Senders should feel free (see what I did there?) to use the language they need to present the sharpest offer possible.