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Avoid Spam Filters: 10 Tips for Surefire Email Deliverability [Slide Show]

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Slide 1 of
110923-01. Intro

Research has shown that one out of every six marketing emails never reaches the inbox because it is mistakenly blocked by a spam filter.

Surprisingly, the sender—not the email service provider (ESP)—has the greater influence on deliverability.

Even though your email solution provider might have an impeccable reputation, your emails may never reach the inbox if your mailing list or content has issues. No software can solve email content or list problems, period. And even the world's most beautiful email is useless if it is blocked or it lands in the junk folder.

Implement the following 10 tips for minimizing deliverability problems, and then compare your results with pre-implementation metrics. You're sure to see a positive effect on your email program and the conversions it generates.

110923-02. 1. Guard your reputation

1. Guard your reputation

Email providers like AOL, Gmail, and Yahoo rate you as an email sender based on the reputation of your domain and Internet protocol (IP) address. For high deliverability, build a positive history by sending only solicited, relevant emails.

If your mailings are too frequent and are frequently unopened, Internet service providers (ISPs) may block your emails.

If you use a professional ESP (such as GetResponse), your risk of being blocked is low. But if you use a dedicated platform, always monitor the reputation of IPs and domains where your email campaigns originate by checking sites such as

110923-03. 2. Keep your list clean

2. Keep your list clean

Purchasing lists of "fresh" email addresses can ruin your deliverability. People respond well only to permission-based emails. Email campaigns sent to purchased lists—which tend to be riddled with dead and inactive email addresses—could damage your reputation beyond repair, leading to domain blocking.

Purchased lists also contain "spam traps"—addresses created to lure spam and generate grounds for nuisance lawsuits.

110923-04. 3. Keep your content clean

3. Keep your content clean

Spam filters look for the following:

  • Frequency of potential spam words (e.g., "free," "bonus")
  • Reputation of links in your email
  • Image-to-text ratio
  • Size of your email
  • Reputation of image-hosting service
110923-05. 4. Choose your 'From' field carefully

4. Choose your 'From' field carefully

Yahoo Mail, in particular, uses a complex algorithm to analyze "from" addresses. During our tests, we've noted different results for the same emails sent using versus

Try tweaking the "from" field address and testing the same content to find out whether a tainted "from" field may be causing problems.


110923-06. 5. Ask recipients to 'whitelist' you

5. Ask recipients to 'whitelist' you

Want to avoid deliverability issues? Simply ask subscribers (at sign up) to whitelist you in their address books. Being on the "allowed senders" list releases you from the constraints of the spam filter.

110923-07. 6. Avoid gimmicks!

6. Avoid gimmicks!

ISPs are wary of senders who use tricks to get email delivered and routinely block the following gimmicks:

  • Hashbusting: Randomly adding certain characters in the subject line or content to fool spam filters (e.g., "F.ree. p.r!z.e")
  • Deceptive subject lines: Starting the email message with "Re:" or "Fwd:" to imply a previous communication initiated by the sender
  • Misleading claims: Using subject lines that state the recipient has won a prize, though the copy lists conditions required to claim it
  • Image text: Cloaking a text message as an image to fool spam filters
110923-08. 7. Eliminate high-risk words

7. Eliminate high-risk words

Minimize the use of words like "free," "prize," and "bonus" in your newsletters. Avoid using too many exclamation marks and all-caps words, especially in the subject line.

110923-09. 8. Monitor your SpamScore Check

8. Monitor your SpamScore Check

A program called SpamScore Check from Spam Assassin tests your emails using many of the same criteria used by ISPs:

  • Risky keywords
  • Blacklisted URLs
  • Text-to-image ratio
  • Many others, updated often as algorithms evolve

Analyze the issues detected by SpamScore Check, and optimize your newsletters to keep deliverability high and safeguard your sender reputation.

110923-10. 9. Monitor your deliverability

9. Monitor your deliverability

Want an easy way to monitor deliverability that costs you nothing? Simply add a list of "seed" email addresses using ISPs your customers use most often (probably Gmail, Yahoo Mail, AOL, and Hotmail).

Create those seed email addresses by setting up five or so mailboxes at each provider, and include those email addresses in your mailing list. After each newsletter is deployed, log in to each seed account and verify whether the email was delivered successfully by that provider. Very useful!

110923-11. 10. Keep in touch

10. Keep in touch

Sending emails once every two or three months can be more detrimental than sending two or three emails per day. Why? Your customers can forget about you.

If they fail to recognize your name in the "from" field, they may delete your messages, hurting your "open" ratio. Worse, subscribers may forget they signed up for your list and so mark messages as spam, generating negative feedback.

Make sure, then, to maintain a steady flow of communication instead of sending infrequent, massive "blasts."

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Maciej Ossowski is director of education at GetResponse, an email marketing provider that serves more than 210,000 SMB customers around the world.

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  • by Anthony Fri Sep 23, 2011 via web

    Point 4 (Slide #5): So what was the result? Did newsletter@ or support@ get a better delivery rate?

  • by Craig Swerdloff Mon Sep 26, 2011 via web

    Great post Maciej! Data hygiene problems are often more complicated than avoiding purchased lists. Consumers often mistype their email address when signing up for a newsletter, and if you are running Cost Per Lead media programs there is potential for Lead Fraud. There are services available for integration directly into your registration form, to validate email addresses in real-time. Consider that "Unknown Users" or dead emails are frequently the biggest cause of deliverability problems.

  • by Maciej Ossowski Tue Oct 4, 2011 via web

    @Anthony: In this particular case, support@ generated a higher inbox placement, but only because it was used extensively in the past by this Customer and it built up a nice reputation.

    When it comes to FROM fields, it's all about using a recognizable address and using it consistently across your mailings. If you swap them frequently, or associate them with emails that generate negative feedback (such as increased spam complaints), you might experience deliverability issues.

    @Craig: Thanks for the kind words! That's a good point. The market for the companies you mentioned is growing and it's absolutely justified. Moreover, there's also a matter a data digitalization. If you take a supermarket chain that processes thousands of printed requests filled out by the store visitors, there's always a risk of inputting lots of bad data and typos into the sytem.

  • by Lynn Mon Oct 10, 2011 via web

    I use ConstantContact and have over 100 rejects from an 800+ email blast. Most are due to spam guards at the recipients.

    I am contemplating forwarding the email blast from my personal email address to the 100+ rejects in hopes of getting around the anti spam measures.

    Any opinions on this approach?

  • by Anthony Mon Oct 10, 2011 via web

    @Lynn: I'm experiencing the same thing with Constant Contact. I have a feeling its because of the rapid expansion of CC and using the same IP for many clients, everyone is being penalized. I'm sure if you ask, they ask if your following best practices. I'm planning to switch to a lesser known service or bring it in house.

    I don't think forwarding from your email will be beneficial.
    a. All of the tracking info is specific to the contact in CC. You won't be able to tell who opens it, who clicks through, who blocked it, etc. All of that data will be linked to your name. If someone clicks on the unsubscribe link - your email is going to be unsubscribed!
    b. It will be a headache managing that secondary list. (removing addresses, updating emails, adding new ones, etc.)
    c. You personal email won't like a 800 email blast out of no where. You risk looking like your account was hacked by a spammer and can get your entire domain's email shutdown.

  • by Maciej Ossowski Tue Oct 11, 2011 via web

    @Lynn: Are your subscribers more in the B2C or B2B sector? It seems to me that it's the second option and in this case your Email Service Provider (ConstantContact) should work with you on an individual basis to solve out these issues.

    At GetResponse, this is handled by a dedicated team of deliverability experts who work with spam filters representatives and mailbox providers in order to troubleshoot any delivery issues.

    The deliverability from your personal account may vary and be even better, but then again you lose all the feedback, tracking, data, segmentation options, etc. so I think it's a not a way to go here.

    @Anthony: Couldn't agree more. Let me know if I can help here.

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