Spam, Outlook, Spam, Microsoft, Spam, Spam, and Spam
Anyone who uses email marketing knows how disastrous it can be to be blacklisted as a spammer. Your emails won’t be delivered, your reputation suffers… not to mention your bottom line.
Fortunately for you, we have tools that report how different email programs evaluate incoming messages. Here are our latest discoveries about how Microsoft Outlook decides what is spam and what isn’t:
- What day your emails go out: Messages sent on a Saturday or Sunday are more closely correlated with spam than messages sent on a weekday.
- UPPERCASE IN THE SUBJECT LINE: If words in uppercase make 25% (or more) of the total number of words, then the email is more correlated with spam. That’s 1 out of every 4 words.
- Symbols (*#&@!!!) in the subject line: A “symbol” is any key on your keyboard that isn’t a letter or a number. Subject lines with 8% (or higher) symbols are more correlated with spam. Spammers used to overuse exclamation points and “@” symbols to get around spamtraps (ever had an email offering you “Vi@gr@”?)… so the traps have evolved.
- Duplicate characters or spaces in the subject line: In many spam messages there is a meaningless (to the recipients) sequence of symbols separated by dozens and dozens of spaces. So emails that have a lot of duplicate characters in the subject line are flagged as potentially being spam.
Of course, this isn’t the complete list of how Outlook evaluates spam — Microsoft isn’t going to release all their anti-spam strategies — but it’s a handy “at-a-glance” list that should get you thinking about your approach and subject lines!
Oh, and have you ever wanted to know why “unwanted email” is called “spam”?
It’s because of this Monty Python sketch:
Probably the only time spam ever made us smile



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Hilarious video Christopher, I actually remember seeing the original airing. Jeez, I’m getting old. lol
Use of a funny video to convey an important message was very clever of you.
Great info & love the vid.
What’s the situation these days with using words such as Free – Offer – Discount etc..
Would love some up do date info on best how to use those.
JP
Hi Jon,
I consulted with our email testing team about your question, and here’s what they said:
“Words in an email are far harder to test. There are a lot of easy-to-find lists of words that are considered spam by blacklist/whitelist organizations, but we don’t have any intell on what Outlook in particular would consider a spam word.”
“Spam filters are always changing, so the best advice is to test everything BEFORE you send it out to your list.”
So there you have it, straight from our testing team to you!