A high email bounce rate casts a shadow over any email marketing campaign.

Even if your opens and clicks are up to par, a high bounce rate raises questions about the quality of your contact list.

More importantly, a consistently high bounce rate can impact the deliverability of future email campaigns. Not only is a certain percentage of your messaging not getting through, future messages to the same email client may receive a higher SPAM-score.

Email bounce rate refers to the percentage of email addresses in your subscriber list that did not receive your message because it was returned by a recipient’s mail server. This includes hard bounces and soft bounces. A hard bounce occurs when an email cannot be delivered at all, as in the case of a fake or incorrect email address. A soft bounce occurs when the server rejects an email due to a seemingly temporary condition such as a full inbox or a connection cannot be established with the recipient’s server.

A certain percentage of emails will always bounce. Fortunately, the goal is reduction, not elimination. Once you understand why emails bounce, you are better situated to improve both deliverability and your overall message quality.

In addition to lead generation and contact data enrichment, LeadGenius manages first touch email campaigns for many of our clients. These are the best practices we follow to ensure the deliverability of hundreds of thousands of emails each month.

If your email bounce rate is over 2%, review these tips for email deliverability and adjust accordingly. These guidelines will help keep more of your marketing and sales messages in the inbox, where you need them to be.


1. Watch Your Language

Most email clients use bayesian filtering to filter out junk emails. Bayesian filtering predicts messages to be spam based on the probability of appearance of different word combinations.

These filters learn to avoid words like mortgage, insurance, casino, viagra, life insurance, and cash bonus. They also look odd formatting and punctuation. For example: H3LLO, ~*Hi*~, $XXX, and F r e e.

You might say to yourself, “I’m a professional. I don’t include language like that in my marketing emails.” Though these examples stick out like a sore thumb, not all language that can score against you is so obvious.

Spam filters frequently penalize legitimate promotional language because of how frequently it appears in junk email. Common marketing and sales messaging like free, act now, limited time, coupons, click now, apply online, giveaway, and sale will all likely count as small strikes against you.

It’s impossible to avoid this type of language altogether, so commit to using it sparingly. These keyword blacklists from Hubspot and MailUp will give you an idea of how broad the range of penalized words is.

If your email reads like an obvious sales ploy to people when they, this will likely be doubly true for the spam filters. Be conscious that the hard sell can penalize you.


2. Ask For Permission

Asking for permission is the best way to ensure deliverability. This isn’t always practical when assembling lists for marketing and sales purposes, but it’s the standard you should seek.

If you implement a double opt-in or email verification step for your email lists, you will likely lose a certain percentage of potential signups. This can be a bitter pill to swallow. Sometimes, up to 20% of initial subscribers fail to complete the second opt-in. This might seem like a big loss, but, the higher percentage of deliverability for the life of that list, plus the increased likelihood that your message will resonate with the contacts on it, makes the initial loss worth it in the long run.

List efficiency is more important than total number of subscribers. An effective list is the one that gets the right message to the right people, not the one that has the most email addresses on in.

Buying a generic list of contacts might get you a few extra opens and clicks in the short term, but it is not worth the decrease in overall email deliverability.

Even if you’re not using a double opt-in permissioning mechanism, it is a good practice to send a confirmation/welcome email. This will provide immediate validation of the new email address and positively reinforce the initial brand experience.


3. Personalize Subject Lines

Emails with personalized subject lines have 26% higher unique open rates than emails with generic subjects, yet 70% of marketers are still not sending personalized emails. If that’s not reason enough personalize, dynamic subject lines can also help deliverability.

Email clients scan for large batches of incoming messages with the same subject line. By adding a personalized field, you cut down on the likelihood that a server will identify your message as overtly promotional. This is particularly relevant if you are sending an email to a large list.

Personalized subject lines can be more than just a First Name field. Company name, city, and job title are some other easy ones to incorporate. When LeadGenius does email prospecting, we sometimes use as many as 3 or more dynamic fields in a subject line. The email itself may contain a dozen or more.

If you need additional inspiration, ExactTarget has a good list of 100 personalized subject lines to get you started.


4. Stop Canvasing

Most webmail services and ISPs use community-based reporting to block spam. If too many of your subscribers click the Report Spam button in their inboxes, that trend is noted and used to determine whether future campaigns are likely to be spam.

This is worth considering in B2B situations where you are potentially sending messages to lots of people at the same company. Company email server far more sensitive to spam.

Consider this: when Joe in the accounting department reports your email as SPAM that was really meant for someone like Tim in Operations, the likelihood that Tim doesn’t get your next email next time around increases.

This is just one more reason to be highly targeted. Canvasing seems like a good idea to incrementally increase returns – the more people who get your email, the more people who will click through, right? –  but it will ultimately undermine deliverability.


5. Offer Plain Text & HTML

Email servers like it when your message has an option for both a plain text and HTML version. There are also a small percentage of servers out there that will only accept plain text.

Most email management tools automatically create a plain text version of your email based the HTML version. However, this is not always the case. For some email software you have to actively enable the plain text feature. This step can often be overlooked.

Before sending, you should always double check to make sure the two versions match.


6. Keep Your Code Clean

Spam filters see emails differently than people.

To you, your email reads like this:

Hi Joe, 

I recently came across the blog post “8 Ways to Reduce Your Email Bounce Rate” that LeadGenius shared on Twitter.

Reducing email bounce rate seems like an interest that we share. In fact, I work for BounceReducer and we help companies like LeadGenius that send lots of emails from multiple domains.

Tom Jones recommended I reach out to you with ideas on how you guys might be able to use our API.

I’d love to get some time on your calendar to discuss these ideas.  Are you available for a 15 minute call on February 24? I look forward to talking soon.

I look forward to touching base,

George Fox


The HTML version should look nice and neat like this:

Example of a well formatted email

Spam filters check for clean code.


However, copying and pasting can result in long string of sloppy HTML. This what a poorly formatted version of  the same email looks like to a spam filter.

sloppy email formatting

Copying and pasting can result in sloppy code.


Long, jumbled code is as unpleasing to spam filters as it is to the human eye.

Having too many images in your email is one of the major factors commonly contributing to bad code. Limit images as much as possible, including in your footer or signature

If you find it preferable to compose in a text editor such as Microsoft Word, make sure you clear the formatting after you paste the draft into your email client.


7. Stay In Touch

All email lists naturally decay.

Individuals are hired and fired. Companies are acquired. New positions are created. Businesses shrink and swell every quarter. Job turnover in some industries is as high 6.5% per month.

Jobs Hires per Month

If you wait 6 months to send an email to a list in a high-decay industry, nearly 40% of the contacts could have gone out of date by the time you press send.

Too many hard bounces is a sign of an old, stale list. Make sure you keep in touch with your subscribers regularly. You should be emailing your list as frequently as you can produce interesting, relevant content. If this is less than every other week, you need to work harder to create relevant content.


8. Manage Your Reputation

“Sender reputation” is as important as it sounds.

Email servers keep track of who is sending undesirable content. Check your domain’s reputation for free with SenderScore. Over 90 is good. 80’s are OK. 70s and below are poor.


A high bounce rate can be a vicious cycle in the sense that domains with a reputation for sending emails with high bounce rates are more likely to be blocked. Return Path reports that 83% of the time an email is not delivered to an inbox, it is due to a poor sender reputation.

Scores are calculated on a rolling, 30-day average. If you have have a low score this can sometimes take months to correct. But, redemption is possible if you start following the above best practices and create messages your recipients are happy to see in their inbox.


Stick to the Fundamentals.

There’s no absolute way to control what your subscribers do with your email or which ISPs hold their feedback against you. But if you take care of your permission-based list, and send relevant content with engaging subject lines, your subscribers are more likely to look favorably on your campaigns and keep their fingers off the spam complaint button.

So, don’t be afraid to say “click here” or talk about certain offers or discounts, if that’s the kind of business you do. As long as the rest of your email is in good shape, spam filters will let you through.