In the early days of email, spam filters were all about the content. Including specific combinations of words and phrases would often make your message more likely to be flagged as spam or blocked outright. As mailbox providers and their spam filters evolved, sender reputation became more important as a factor: instead of a single message, providers evaluate a sender’s “body of work.” Senders whose messages often generate spam complaints or are ignored by recipients are now the most likely to end up in the dreaded spam folder. Message content still factors into many spam filters, but is almost always outweighed by IP or domain reputation.
Even so, many in the industry remain convinced certain words or phrases are the kiss of death for an email. You can find recent articles advising marketers to avoid including words like “free” in the subject line, along with symbols like dollar signs or exclamation points. It’s not hard for senders to get confused with the seemingly conflicting information out there, so we wanted to investigate how it all might tie together.