What went wrong? It could have been one big thing; it could have been a number of little things that collectively raised a big red flag. The good news is that if you know beforehand what causes a message to be labeled as spam, you can save it from that giant black hole.

Points of possible rejection

Today's email technology allows many points for interaction before a message ever even arrives in a receiver's inbox. The potential "dead ends" or "filter points" that can kill your message fall into four broad categories:

• Internet-based filters
• Internet service providers (ISPs)
• Corporate infrastructures
• Personal email clients

Your message may be stopped at any of these points for a variety of reasons. It may be that you included specific words in your message, or it could be that your "from" address is objectionable. Your IP address may be blacklisted, or you may have included attachments, not realizing that many organizations don't let ANY mail through with attachments of any kind. Finally, if you do make it to the inbox, the format of your email could get your message junked at the personal email client level. Here are some tips to help you avoid most of the major mistakes.

Killer subject line mistakes

It's likely that you've received enough spam to know some of the tricks spammers use in their subject lines - replacing letters with characters, placing an RE: in there so you think it's a response to a message you've sent previously, misspelling words, etc. While you may not be mimicking these specific tricks, you may be committing similar sins unwittingly because of how your subject line is worded. Here's how to ensure your subject line doesn't raise warnings:

• Don't use an exclamation point.
• The use of all caps, even if it's just one word, is a red flag.
• Don't deliberately misspell words (and don't do it accidentally either).
• Avoid non-standard characters. For example, your brand name does not need a registration mark in the subject line despite what the legal department may say.
• Only use necessary punctuation. In most cases, at most you might need a comma or dash.
• If you're using an apostrophe, make sure it's straight, not "smart." And don't copy any such punctuation from Microsoft Word to paste into your subject line - these are non-standard characters.
• Avoid "spammy" (not sure if this is a word, but it should be) words (see the list below, shown here as an image; otherwise, this email would most likely never make it into your inbox).

Crushing content blunders

There are three things to keep in mind when creating your message content to avoid spam issues. One is the wording you are using, and you just might be surprised. Some words that you wouldn't necessarily associate with spam will nevertheless score points against a spam filter. Here are some words worth avoiding:

The second thing to examine is your html (unless a message creation system, like SubscriberMail, is creating the html for you). Mis-formatted html can get your message blocked every time. Make sure your html is clean, and avoid the following:

• extra or unnecessary tags
• heavy use of images versus text
• using non-standard Web fonts
• using text that's the same color as the background

Finally, never send attachments of any sort, including PDFs. Not only can they appear suspicious to a spam filter, but an attached file has no trackable action so you have no way of knowing if someone opened your attachment or not. Instead, include a link in your email to the file you want people to see. This way you will not trigger any filters, and you will be able to tell from your click-through details how many recipients viewed the file.

Keep it clean - your list, that is

The importance of a clean list can't be stressed enough. A large number of repeated bounces or complaints is a surefire way to get blacklisted. Ensure your list is as clean as possible by making sure that:

• hard bounces are removed,
• unsubscribes are removed within 7 days (this is also required by law, though removing immediately is preferred), and
• you are using a strict opt-in-only process.

"I'm on the list"

Think of a bouncer at a popular club. If your name is "on the list," you'll get in with no questions asked. So make a continual effort to get recipients to add your email address to their address book or safe list. You can present this request during the opt-in process when subscribers are maximally tuned in to ensuring receipt of your email. It is especially important that you include this request in your initial welcome message.

And finally, you should add it to the top of all email communications. This can be something simple, such as: "Please add companyname@emailaddress.com to your address book to ensure messages from Company Name are delivered to your inbox."

Protect your Rep

Arguably, if you are taking all these steps, your reputation as a responsible emailer should not be tarnished. Once you have established yourself as a responsible email marketer, you can use this reputation to your advantage. Gaining whitelisted status with ISPs or becoming a Certified Sender through Return Path are a couple examples. These practices will help ensure that your messages are delivered to the intended reader's inbox. All this is important, because reputation is gaining favor with ISPs as a critical factor in deciding which emails to deliver and which emails to block.

By addressing these five areas when planning your next email campaign, you can make sure that you aren't accidentally perceived as a spammer. This will not only help ensure your messages are delivered, but will also help ensure that you're sending relevant information to the right people in a way that is not bothersome.