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May 12, 2016 // 8:00 AM

A Marketer's Guide to Email Deliverability: How to Avoid Email Spam Filters

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Marketers spend a lot of time drafting poignant email copy, designing wonderfully branded email templates, and crafting succinct and enticing email subject lines that get open and click-through rates skyrocketing.

But before hitting send, have you considered whether your subscribers will even get the opportunity to read your email?

No matter how legitimate of an email marketer you are, there are a host of things you may not even know about that can prevent your email from ever reaching someone's inbox. With more stringent laws and increasingly sophisticated spam filters, it's to your benefit to know everything that can affect your email's deliverability. Download our free guide to creating emails people actually click here. 

If steering clear of legal trouble isn't enough to convince you, squeezing more ROI out of your email marketing efforts certainly should. Take a look at the things you should absolutely never do in your email marketing if you want your messages to be successfully delivered, and the things you can proactively do to increase your rate of email deliverability. (Take HubSpot's free email marketing certification course to learn even more about email marketing best practices.)

29 Ways to Avoid Sending Spam Email & Improve Your Email Deliverability

What You Should Never Do

1) Don't buy or rent email lists.

Yes, you can legally rent and purchase lists of people who have agreed to email communications -- but it's never a good idea. Not only is it a dirty email marketing tactic that goes against the Terms of Service for your email service provider, but these people don't actually know you -- and it's likely they won't even want your emails. In other words, there's a good change they'll mark you as spam. Plus, let's be honest ... high quality email addresses are never for sale.

2) Don't scrape sites for email addresses.

Scraping websites for email addresses may seem like a fast way to build a contact list, but it's bad for your business -- not to mention illegal in many countries, including the United States, thanks to the CAN-SPAM Act.

3) Don't email people who have bounced repeatedly.

Hard bounces are the result of an invalid, closed, or non-existent email address, and these emails will never be successfully delivered. Bounce rates are one of the key factors internet service providers (ISPs) use to determine an email sender's reputation, so having too many hard bounces can cause them to stop allowing your emails in folks' inboxes.

(Email deliverability is covered extensively in HubSpot's free email marketing certification course, so check that out to learn more.)

4) Don't use all caps anywhere in your email or its subject line.

Don't yell at people. It's not nice. Using all caps in your subject line might get the recipients' attention, but probably not in a good way. Using all caps can really rub people the wrong way. It's annoying and can seem spammy.

In fact, according to a study by the Radicati Groupmore than 85% of respondents prefer an all-lowercase subject line to one in all caps. 

Instead of using disruptive tactics like all caps to get people's attention, try personalizing your emails, establishing relevancy, and using catchy and delightful language. (Read this blog post on how to write compelling emails for more tips.)

5) Don't use exclamation points!!!!!

Another thing that can make your subject line and/or email look unprofessional and spammy? Exclamation points -- especially a whole bunch of them in a row. And when 69% of email recipients report email as spam based solely on the subject line, you'll want to stay away from triggers like this as much as you can.

Plus, when you ask punctuation to do a word's job, it can really dilute your message. The next time you're tempted to use an exclamation point in an email (or anywhere, really), use this flowchart, "Should I Use an Exclamation Point?", as a gut check.

6) Don't use video, Flash, or JavaScript within your email.

By default, most email clients don't allow the ability to view rich media like Flash or video embeds. Instead, use an image of your video player (with a play button) that links to the rich media on a website page.

As for JavaScript and other dynamic scripts, even if a spam filter allows your email through, most email clients won't allow these scripts to function -- so avoid using them altogether.

7) Don't embed forms in your emails.

Forms aren't supported in email across common email clients due to security risks. Instead, place a call-to-action button or a link to a landing page with a form in the body of your email.

(HubSpot customers: Learn how to add a call-to-action button to your emails in HubSpot here, and how to create a form for your landing pages in HubSpot here.)

8) Don't include attachments to your emails.

If you want to send your recipients something like a PDF or a Word document, don't attach the file to the email -- otherwise your email could get blocked by spam filters. Instead, upload the attachment to your website and link to the file location in your email using an effective call-to-action button. This'll minimize the chance of being blocked by spam filters and decrease the load time of your email.

(HubSpot users: HubSpot's attachment tool in the email editor automatically does this for you. Simply highlight a bit of text or an image and click the attachment icon, and HubSpot will turn that text or image into a link leading to that attachment.) 

9) Don't use spam trigger words.

One of easiest ways to avoid spam filters is by carefully choosing the words you use in your email's subject line. A good rule of thumb is this: If it sounds like something a used car salesman would say, it's probably a spam trigger word. Think "free," "guarantee," no obligation," and so on. (For more, look at this list of common spam trigger words.)

Instead of using these trigger words, be creative, interesting, and informative -- without giving too much away. Some better ideas for subject lines include:

  • "Hi [name], [question]?"
  • "Did you get what you were looking for?"
  • "You are not alone."
  • "Feeling blue? Like puppies?"

10) Don't use a red font when drafting your emails.

Same goes for using invisible text, i.e. a white font on top of a white background. These are common tricks that spammers use, so it's an instant red flag for spam filters. 

In fact, people don't like when marketers use irregular fonts, font sizes, and font colors at all in emails. In that same study by the Radicati Group, out of the top 10 objectionable email trends, four revolve around fonts. Over 60% of respondents considered it unacceptable for email marketers to use different font sizes, irregular fonts, and different font colors. Nearly 70% of respondents prefer fonts to be one size.

11) Don't forget to use spell check.

According to that Radicati Group study80% of all respondents find spelling and grammatical errors the most unacceptable email offense. But spelling mistakes aren't just unprofessional -- they're actually a spam trigger, too.

It's easy for little spelling mistakes to slip by -- especially when you're self-editing. Read this post to learn the most common spelling and grammar mistakes so you never make them again.

12) Don't jam pack your email copy with keywords.

Keyword-stuffing your emails means shoving as many keywords into your emails as you can. There's a reason Google give a lower rank to webpages that are stuffed with keywords -- and that's because it's harmful to user experience. No one wants to read content that's optimized for a robot.

To make it more likely folks will open your emails and not mark them as spam, write your emails for humans, not robots. Copywriting that makes people want to take action is both simple and compelling. To make your writing sound more personable and relatable, use casual language, colloquial expressions, and even personal anecdotes.

I love the example below from Turnstyle Cycle (from our roundup of 12 great email marketing examples). The copy is beautiful in its simplicity. It's friendly, yet sincere -- especially with the following lines:

  • "We know you are busy and would hate to see you miss out"
  • "Please let us know if we can help accommodate in any way possible"
  • "Feel free to give us a call - we want to help :)"

Plus, they provided me with the exact details I needed to know -- a reminder of what I'd signed up for and when, the expiration date, and a phone number to reach them. Check it out:

turnstyle-email-copy-example.png

13) Don't use an overwhelming number of images, or huge images.

Using one large image as your entire email, or too many images in general, tends to end up in recipients' spam folders.

You'll also want to make your image file sizes as small as possible without losing their visual integrity to prevent long email load times. (If you're a HubSpot user, the email tool automatically compresses images in emails so they load faster. For non-HubSpot users, some good image compression tools include Compressor.io, Compressjpeg.com, and Jpegmini.com.)

Not to mention, Microsoft Outlook doesn't recognize background images, so you may want to avoid those and use a background color instead.

What You Should Do

14) Do keep your email lists current & clean.

Even if your list is entirely built on valid opt-ins, you are at risk of being branded a "spammer" if you don’t practice proper email hygiene. Why? Because internet service providers (ISPs) base complaint rates on active subscribers, not total subscribers.

Also, expired email addresses can turn into SPAM traps, meaning that even if you acquired emails in a legitimate manner, the abandoned addresses that haven't engaged in years may have morphed into spam traps. Hitting even just one spam trap can cause deliverability problems.

Expired email addresses can also turn into unknown users (bounces). If you hit unknown accounts at a rate higher that 5%, then ISPs are going to see you as someone who has really bad email hygiene. The result? They'll make it harder for your emails to reach people's inboxes, and your overall sender reputation will definitely drop -- leading to even more trouble reaching people's inboxes.

By keeping your email lists current and clean, you'll decrease the likelihood people will flag your emails as spam. You can identify inactive subscribers and expired email addresses with metrics such as opens, clicks, or website activity. 

15) See if you can reengage inactive or infrequently active subscribers.

"Graymail" refers to email people technically opted in to receive, but don't really want, leading them to become less active or inactive altogether. Although it's not considered spam, sending graymail is problematic because it can hurt the deliverability of your email overall. Tipped off by low engagement rates, ISPs and inbox providers may deliver email from known-graymail senders straight to recipients' "junk" folders -- so the email technically gets sent (and can even appear to have been delivered), but it's not necessarily seen.

Keep track of your inactive and infrequently active subscribers, and develop re-engagement campaigns for contacts who have stopped engaging with your messages. For example, you could set conditions such as the length of time since their last form submission, website visit, or email click, triggering the email when it's been a while since a contact last engaged with you.

In your workflow, you might try sending them an exclusive offer or coupon to get them excited about your company again. Or, you might ask them for feedback by sending out a quick survey to see what they would like to see in your emails. (Read this blog post for more ideas for launching an effective email re-engagement campaign.)

16) Do use double opt-in.

Double opt-in means that after someone subscribes to your email list, you send them a follow-up email with a confirmation link ensuring they actually want to receive email communications from you.

Users that have to confirm that they want email communications from your company are the ones that will fully read and engage with the emails they receive from your business. When you use double opt-in, your email lists will be much more qualified and your subscribers much more engaged. (HubSpot customers: Learn how to set up double opt-in in HubSpot here.)

17) Do ask your subscribers to add you to their address book.

Spam filters are more aggressive than ever -- so much so that sometimes, the emails people value and want to read still end up in their spam boxes.

But most spam filters allow you to whitelist a sender by adding their email address to their email's address book. When subscribers add you to their address book, spam filters will back off. 

18) Do include a clear unsubscribe link and a physical mailing address in your email footer.

Allowing people to unsubscribe is important for list hygiene because anyone receiving your emails should actually want to receive them -- otherwise, you're just spamming them. But did you know that it's illegal to not have a way for your recipients to easily unsubscribe in many countries, including the United States?

In your marketing emails, you must include a way for folks to unsubscribe from your email list, either by simply sending a reply email or by clicking no more than one level deep to reach a page from which they can unsubscribe. Which method you choose is entirely up to you, as long as the information is clear and easy to locate.

The most common place for these unsubscribe CTAs is in the footer of your email, so users tend to know to look for it there -- which makes for a better user experience. Here's an example from one of HubSpot's emails:

unsubscribe-1.png

In addition to the unsubscribe link, include a link to update subscriber preferences, which you can also see in the example above. That way, recipients can unsubscribe from just one type of email instead of all of them.

19) Do honor unsubscribes.

If someone unsubscribes, they must come off your email list. It's the law. This should go without saying. Check out this list of effective unsubscribe pages to make the unsubscribe process a little more delightful for recipients.

This is where email marketing software that integrates seamlessly with your CRM comes in handy -- because any unsubscribes are immediately processed and recorded in both the contact record and within the email software. (But if you're removing unsubscribed addresses from your list manually, make it a top priority to process that request.)

20) Do use a familiar sender name.

Because people are so inundated with SPAM, they hesitate to open email from unfamiliar senders. Make sure recipients can recognize you in your sender by using your brand name.

Better yet, send the email from a real person. Recipients are typically more likely to trust a personalized sender name and email address than a generic one. At HubSpot we found that that emails sent from "Maggie Georgieva, HubSpot" perform better in terms of open and clickthrough rate than emails sent from just "HubSpot." (HubSpot customers: Learn how to personalize the "From" name and email address here.)

21) Do include your recipient’s name in the "To:" field.

This way, spam filters know that you do, indeed, know your recipient. Plus, personalizing your emails around your contacts can also be vital to their engagement with your content.

22) Do offer both an HTML and a plain text version of your emails.

Plain text emails are simply emails void of any formatting, while HTML (HyperText Markup Language) emails use formatting that let you design more beautiful emails with attractive visual components. By offering both a plain text and HTML version of a single email, you're not only indicating your legitimacy to ISPs, but you're also making your emails more reader-friendly.

Most email marketing tools will let you easily create plain-text versions within their email editor, so take those five extra minutes to create and optimize the plain-text version of your email. (HubSpot customers: Learn how to create a plain-text email in HubSpot here.)

Also, make sure the HTML version is properly coded: If there are broken tags in your HTML, the email provider and users might mark it as spam. 

23) Do allow people to view your email in a web browser.

Even after every step is taken to assure proper email design, an email client can still display an email poorly. Include a link in every email to view the email as a web page. (HubSpot customers: Learn how to do this easily in HubSpot here.)

View-As-A-Web-Page-Link-1.png

24) Include alt text in your email images.

Many email clients block images by default. This means that when someone opens your email, the images won't load unless they click a button to show them or change their default settings. Adding alt text to your images helps recipients understand your message even if they can't see the images.

This is especially bad if you use an image as a call-to-action. Without alt text, a "turned off" image will look like this:

When you add alt text to the image, recipients will still know where to click to complete the action:

This is what an image with alt-text looks like.

You can either edit the alt text in your email tool's rich text editor (just right-click the image and edit away), or you can manually enter it in the HTML editor of your email tool like this:

<a href="HTTP://YOURLINKHERE.COM"><img class="alignCenter shadow" src="YOUR CTA BUTTON IMAGE SOURCE HERE.JPG" alt-text="YOUR ALT-TEXT GOES HERE"/></a>

25) Do keep emails short.

Too much copy is another red flag for spam filters. Not only that, but people generally like concise emails better. Everyone's busy and their inbox is already full, so why make things worse?

One of the best ways to keep things short and sweet is to write like a human. Writing your email like you were talking to someone in real life makes it feel much more approachable and relevant. (Read this blog post on how to write compelling emails for more tips.)

If you do have to write a lengthier email, then break it up into multiple paragraphs. Giving visual breaks and composing the email with a clear introduction, middle, and conclusion will make it much easier on your reader.

26) Do test emails before sending them.

There are a lot of email clients out there these days that email marketers have to consider when creating emails. On top of that, we have to consider mobile users, too -- after all, 53% of people read email on their mobile devices.

It turns out each of these clients displays emails differently. While it may be time-consuming to test out your emails for all email clients, you'll want to test them for the ones your audience uses the most. According to Litmus' research of 1.06 billion email opens, the top five email clients are:

  1. Apple iPhone's Mail app (28% of users)
  2. Gmail (16% of users)
  3. Apple iPad's Mail app (11% of users)
  4. Google Android's Mail app (9% of users)
  5. Outlook (9% of users)

If your email marketing tool lets you, go ahead and preview what your email looks like in different email clients and devices that are popular with your audience. (HubSpot customers: Use our Preview in other inboxes feature to send a test email and see how the design of your email looks in each email client.)

You should also send out a test version of your email before you send out the real deal to ensure it's working properly. (HubSpot customers: Learn how to test your emails here.)

27) Do get email sender accreditation from a third party.

Sender accreditation is a third-party process of verifying email senders and requiring them to follow certain usage guidelines. In return, you'll be listed in a trusted listing that ISPs reference to allow certain emails to bypass email filters.

28) Do monitor your sender reputation.

Your emails' deliverability depends largely on your IP address' reputation. If you're sending email from an IP address with a poor reputation, your emails are far less likely to be successfully delivered to senders' inboxes.

DNSstuff.com lets you check on whether or not you are a blacklisted sender -- something many unlucky email marketers aren't even aware of.

29) Do stay up-to-date on changes in email sending laws, ISP behavior, and spam filter technology.

Email marketing is constantly evolving, and staying in the know helps ensure you’re always following best practices -- and the law. Responsible and legitimate email marketers make a point of regularly reading up on email sending laws, ISP behavior, and spam filter technology. If you're looking for more information, check in with your company's legal department or a trusted lawyer to ensure you're staying within the boundaries of the law. Want to learn more about email deliverabilty? Watch class six in our HubSpot Academy's Email Marketing Certification course taught by HubSpot's Post Master, Tom Monaghan.

What other techniques not included on this list do you use to increase your rate of email deliverability? Share with us in the comments.

Editor's Note: This post was originally published in January 2012 and has been updated for freshness, accuracy, and comprehensiveness.

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