Even valid emails bounce sometimes. But, why?

You think you’ve done everything right: your message is relevant, the formatting is clean, your recipients have all opt-ed in. And yet, your email blast always comes back with what seems like a lot of bounces.

What are you doing wrong? The answer could be “nothing.”

Some bounces are inevitable. A marketer’s goal is reduction, not elimination. What matters is that you’re consistently improving.

A variety of factors contribute to overall email deliverability. Even permission-based email marketing services such MailChimp that require two-step authentication estimate that 10-20% of all email sent from their system are blocked from subscribers’ inboxes.

The first step towards reducing your bounce rate for sales and marketing emails is understanding why some emails don’t make it to the inbox.

1. Increasingly Aggressive Spam Filters

The SPAM war is an escalating arms race.

SPAM filters constantly improve their algorithms to filter out unwanted messages, and spammers devise new ways to get past them.

84% of all email is SPAM. – The Radicati Group

Incidentally, corporate spam filters and email firewalls are treating a larger amount of identical incoming emails as SPAM in an effort to filter out the junk.

Certain industries see higher rates on average than others. You should know where you stack up against the competition. Are you out-pacing the averages for your industry or falling behind?

bounce rate for mailchimp and constant contact

Compare the self-reported bounce rates of two popular email marketing services, MailChimp and Constant Contact. Some industries experience consistently higher bounce rates than others.

[Tweet “84% of all email is SPAM -@radicatigroup”]


2. Individual Server Administrators

Server administrators check every incoming email and assign it a SPAM score.

SpamAssassin is a popular tool frequently used to identify unwanted messages by scanning and evaluating all the content in an email message. The list of criteria provided to score emails as SPAM is always getting longer and longer. 

It’s obvious why the phrase “Fast Viagra Delivery” is a strong indicator of a SPAM message. However, there are many factors used to negatively score emails that could easily appear in a legitimate marketing email. 

Here are a few SpamAssassin descriptions of the criteria that can count against you:

Subject starts with “Free”

Contains, “If you want to subscribe…”

Offers a full refund

Claims you have provided permission

“See for yourself”

Subject is all capitals

Message is 0% to 10% HTML

HTML title contains no text

“Free Preview”

Individual server administrators determine what constitutes a passing grade, so what gets by some filters does not pass all of them.


3. Natural Database Decay

Email lists are continually rusting. Individuals are hired and fired. Companies are acquired. New positions are created. Businesses shrink and swell every quarter.

Jobs Hires per Month

Because of natural list decay, a certain amount email address will fail.

If your monthly industry hire/separation rate is 4.5%, and you don’t email a particular list for 3 months, then potentially 12.9% of your contacts may have left their company by the time your next email blast goes out.


4. Temporary Un-deliverables

A soft bounce occurs when the server rejects an email due to a seemingly temporary condition such as a full inbox, a connection cannot be established, or the email is too large. 

Some email services distinguish between hard vs. soft bounces in their reporting. Others do not.

Most email services will attempt to resend messages that soft bounce. Hubspot, for example, will attempt to resend emails that have soft bounced for up to 72 hours until the message is either successfully delivered or it fails permanently.

Accordingly, bounce rate for an individual campaign may go up or down in the days following an email blast.


5. Invalid Addresses

A hard bounce occurs when an e-mail message is returned to the sender because the recipient’s address is invalid. A hard bounce can occur because the domain name doesn’t exist or because the recipient is unknown.

This usually happens for one of two reasons: fat fingers or deliberate deception.

Remember, there’s no spell check for email. Typing mistakes occur frequently. The individual themselves could have made a mistake when signing up, your salesperson could have mistyped the address when entering it into your CSM, or the 3rd party you acquired the list from made an error.

There’s also a chance that the contact gave a false email address, which can be the case if you’re offering something online, such as a piece of content, in exchange for an email.


6. Sender Reputation

A good reputation is more valuable than money. – Publilius Syrus

A spam filter’s job is to rate how familiar or relevant you are with your recipients. Sender Reputation is the most important factor used to determine email acceptance by an ISP.

A sender’s reputation is monitored by a variety of factors and is linked either to the domain or the IP address from which the emails are sent or a combination of both. ISPs often use external companies to provide sender reputation data so that they can screen emails against it.

Check your own domain reputation using a free tool like Return Path’s SenderScore or McAfee’s TrustedSource.


7. Blacklisted IP Ranges

Spam filters check your sending IP against blacklisted IP ranges. Unfortunately, that means if anyone in your IP range is spamming, your legitimate messages can get trapped in filters as well.

As the old saying goes, you’re only as good as the company you keep.

For example, if one of the millions of users of Infusionsoft or Aweber is doing something spammy, it can temporarily affect the deliverability of other users. This is why email services work so hard to make sure their users operate within their terms of service.

On a smaller scale, if the marketing department at your company is abusing your email client, this could affect deliverability for your customer service emails.

Repeat offenders can end up on permanent blacklists. In all likelihood, if you’ve been permanently blacklisted, you’d know. But, if you’re still curious, check your domain on Debouncer which monitors over 100 different blacklists.


8. Evolving Industry Standards

The list of what qualifies as “spammy” changes often.

DMARC, which stands for “Domain-based Message Authentication, Reporting & Conformance”, is a technical specification created by a group of business and organizations that want to help reduce the potential for email-based abuse.

DMARC companies and industries

DMARC participants


[Tweet “838 billion marketing emails were sent in 2013. – @Forrester”]

Each year, there is a DMARC conference to establish best practices to protect consumers from annoying and dangerous emails. DMARC is primarily concerned with email spoofing – the creation of email messages with a forged sender address – but updates to their best practices can also affect bounce rates.

 Read The Follow Up Post “8 Ways To Reduce Your Email Bounce Rate”

Links/ Additional Resources

“About SPAM Filters” from the MailChimp Knowledge Base

The average open, click-through, and bounce rates of other Constant Contact customers by industry, Constant Contact