Often we write emails to our clients or prospects and use a variety of words that will land you in Spam Jail if you aren't careful
I have looked around the web for the most comprehensive collection of these and think that Hub Spot offers the best list
The Ultimate List of Email SPAM Trigger Words
While many in the industry would say something like: "ISPs have been using an IP based reputation method for quite some time
and have more recently been adding in domain reputation, too, so it's a
combination of many things; not just a list of words to avoid." Believe me the use of words matters.
Mailchimp a respected email company has a nice article that provides an overview of how to keep your stuff out of the dustbin
http://kb.mailchimp.com/article/how-spam-filters-think
Other issues to consider are
Number of links. Are your links hidden or not. What domain and email address are you coming from or are you using someone like MailChimp... all of this matters but it first starts with email copy and the words you choose both in the header (subject) and the body.
For those of you interested in more depth the open source Spam Assassins list is here with descriptions on each of the particular issues any email might have.
http://spamassassin.apache.org/tests_3_3_x.html
