Reasons Emails Bounce

Reasons Emails Bounce


Even after doing everything right, email blasts may come back with what seems like a lot of bounces. A variety of factors contribute to email deliverability. The first step towards reducing the bounce rate for sales and marketing emails is understanding why some emails don't make it to the inbox. This article explores likely reasons for email bounces.

1. Increasingly Aggressive Spam Filters

SPAM filters constantly improve their algorithms to filter out unwanted messages, and spammers devise new ways to get past them. Incidentally, corporate spam filters and email firewalls treat many identical incoming emails as SPAM to filter out the junk.

2. Individual Server Administrators

Server administrators check every incoming email and assign it a SPAM score. The list of criteria provided to score emails as SPAM is always getting longer and longer. However, many factors negatively score emails that could easily appear in a legitimate marketing email. Here are few descriptions of the criteria that can count against you:
  1. The subject starts with "Free."
  2. Contains, "If you want to subscribe..."
  3. Offers a full refund
  4. Claims you have provided permission
  5. "See for yourself."
  6. The subject is all capitals
  7. Message is 0% to 10% HTML
  8. HTML title contains no text
  9. "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

A database of emails needs to be constantly maintained and updated. Unfortunately, email lists are continually rusting. Prime examples are company acquisitions and people switching employers. In addition, businesses shrink and swell every quarter. Because of natural list decay, a certain amount email addresses will fail.

4. Temporary Un-deliverables

A soft bounce occurs when the server rejects an email due to a seemingly temporary condition. Likely causes are a full inbox, a connection that cannot be established, or too large an email. Some email services distinguish between hard vs. soft bounces and notify the user. Others do not. Most email services will attempt to resend messages that receive a soft bounce. Accordingly, the 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 email message is returned to the sender because the recipient's address is invalid. For example, a hard bounce can occur because the domain name doesn't exist or the recipient is unknown. Hard bounces usually happen for one of two reasons: fat fingers or deliberate deception.

There's no spell check for email. Typing mistakes occur frequently. The individual could have made a mistake when signing up. A simple typo into the CSM 
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 spam filter's job is to rate how familiar or relevant you are with your recipients. Sender's reputation is the most important factor used to determine email acceptance by an ISP. Various factors monitor a sender's reputation. For example, the domain or the IP address from which the emails are sent or a combination of both are compromised. ISPs often use external companies to provide sender reputation data so that they can screen emails against it.

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.
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. 

8. Image To Text Ratio

While Image-to-text ratio is important, there is not an exact formula that works effectively under all circumstances.  However, there are some rules of thumb that are considered best practices. A minimum of 60% text and a maximum of 40% image coverage, with at least 400 characters of text is recommended. However, tests showed little effect on deliverability when the image ratio was greater, providing that other reputation and deliverability factors were good. 

Best practice recommendations
  1. Strive for a good balance of text and images in a way that makes sense for your business.
  2. Use enough text in the body of the message so subscribers get a sense of the message content whether images are on or off. Many email clients have images turned off by default, so an image heavy email with little text may not get a good subscriber response.
  3. Use descriptive alternative text (alt text) with images to help subscribers get a sense of the message content with images off.
  4. Favor a heavier use of images for emails targeted at a mobile viewership, since they make great tap targets.
  5. Send a test email to Inbox Preview before deploying to your subscribers to get data on spam filter performance.
  6. Test different image-to-text ratios to determine what works best for your business.

The below mentioned articles may help you to overcome the obstacles of the email bounces:

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