What happens when your email bounces?

 In Developer, Email Deliverability, Email Infrastructure

You know how email works.

When you hit the Send button, your email passes through several servers, gets into a queue waiting to be processed and finally reaches the destination. It doesn’t always reach the intended destination. When you view your real-time reports on Pepipost, you’ll realize that some emails have ‘bounced’.

What do you mean by email bounce?

An email that cannot be delivered to the intended recipient is labeled as “bounced”. At Pepipost, there are two types of bounces we report.

  • Soft (temporary) bounce: In this case, even though the email address is recognized by the recipient’s mail server, the email cannot be delivered and is returned back to the sender. There could be many reasons for this – mailbox full, message too large, mail server temporarily unavailable, etc.
  • Hard (permanent) bounce: Occurs when recipient email address is invalid/terminated or when the domain name doesn’t exist. While most cases of hard bounce occur due to invalid email address, there may be instances when emails get rejected because you haven’t done SPF configuration on your DNS account. You need to define IP in TXT records to allow Pepipost servers to send emails on your behalf.

Do email bounces need to be managed?

Email marketers mostly focus on only open and click rates whereas looking at bounces is like gazing at a crystal ball – warning you of impending deliverability issues.

While a soft bounce is not critical and the message does get delivered at a later point in time, hard bounce plays an important role in your email deliverability and needs to be closely monitored and managed. Bounced emails should be under 5% of the total emails sent and anything over 10% is a red flag that should be investigated.

How do you know why exactly your email got rejected?

The response from remote server gives good insights as to why an email could not be delivered to a particular recipient.
1.If the Email Address is disabled by Gmail or User himself. The bounce notification will look something like this:
The response from the remote server was:
550 5.2.1 The email account that you tried to reach is disabled. Learn more at https://support.google.com/mail/?p=DisabledUser17si15813694wmv.65– gsmtp
Final-Recipient: rfc822; clairepetersen086@gmail.com
Action: failed
Status: 5.2.1
Remote-MTA: dns; gmail-smtp-in.l.google.com. (2a00:1450:400c:c04::1a, the
server for the domain gmail.com.)
Diagnostic-Code: smtp; 550-5.2.1 The email account that you tried to reach is disabled. Learn more at 550 5.2.1  https://support.google.com/mail/?p=DisabledUser 17si15813694wmv.65 – gsmtp
Last-Attempt-Date: Wed, 01 Mar 2017 02:22:32 -0800 (PST)

2. If the Email Address doesn’t exist at all i.e. INVALID then the bounce notification will look something like this:
The response from the remote server was:
550 5.1.1 The email account that you tried to reach does not exist. Please try double-checking the recipient’s email address for typos or unnecessary spaces. Learn more at https://support.google.com/mail/?p=NoSuchUser k98si4186592wrc.76 – gsmtp
Final-Recipient: rfc822; pepipostsmail@gmail.com
Action: failed
Status: 5.1.1
Remote-MTA: dns; gmail-smtp-in.l.google.com. (2a00:1450:400c:c0b::1a, the
server for the domain gmail.com.)
Diagnostic-Code: smtp; 550-5.1.1 The email account that you tried to reach does not exist. Please try
550-5.1.1 double-checking the recipient’s email address for typos or
550-5.1.1 unnecessary spaces. Learn more at
550 5.1.1  https://support.google.com/mail/?p=NoSuchUser k98si4186592wrc.76 – gsmtp
Last-Attempt-Date: Wed, 01 Mar 2017 02:24:28 -0800 (PST)

In both of the above cases, the emails are being rejected and the recipient server (here in this case it’s Gmail), returns a 550 series permanent fatal error:

In case I: 550 5.2.1 The email account that you tried to reach is disabled. Learn more at https://support.google.com/mail/?p=DisabledUser17si15813694wmv.65 – gsmtp.

In case II: 550 5.1.1 The email account that you tried to reach does not exist. Please try double-checking the recipient’s email address for typos or unnecessary spaces. Learn more at https://support.google.com/mail/?p=NoSuchUser k98si4186592wrc.76 – gsmtp

For your reference, here are the other types of Gmail Error Messages: https://support.google.com/a/answer/3726730?hl=en

How Google (and other ISPs) decide the fate of your email

You may have observed one more parameter that Gmail is recording: Last-Attempt-Date.

This is very critical. The Date/Time when you last attempted to send email to an email address is recorded. Along with this, the IP address, sender domain and other message details/patterns are being recorded. Notice these scenarios:

  1. Google will observe if you are making multiple attempts to same email address. A person having in-house infrastructure to send emails would have no way of knowing that the email bounced and would continue to send emails to that email address. Even if the in-house system is smart enough to track the bounces, you wouldn’t know about the type of bounces and hardly any take action on these bounced email addresses.
  2. Some use multiple ESPs to send their emails. While ESPs have a mechanism to block the hard bounce email addresses, they would no way know that the email address was blocked by the other ESP and this way attempts to that particular email address happens through multiple pipes.
  3. You change the sender domain frequently to bypass the Anti-Spam filters. But, Spam Filters are smart. They even track the pattern of the content too.

“Instead of every time putting efforts to hack Anti-Spam filters with your smartness, try to incorporate the best email practices.”

Google tracks how hard bounce email addresses are managed. If you send too often with the same message style or source IP or sender domain, it will consider your mails as spam, aggravated by the fact that you are ignoring the bounce errors. Soon you’ll get blocked from sending to any other email address for a certain amount of time from your IP address used to send the mails. This can last for couple of days or even up to a month, depending upon the severity.

Poor management of hard bounces will affect your sender domain reputation and also the delivery IP address of the ESP.

So, next time you send emails, beware of bounces. It is always recommended to suppress your hard bounces as soon as you are notified, so that no second attempt is made on same email address and the chances of hitting blacklist decreases.

Pepipost is on a mission to build a cleaner email eco-system and are putting efforts to bring awareness and encourage good email sender practices.

As a Global Email Service Provider, we keep our policies compliant with other ISPs and Anti-spam filters. In case you are using Pepipost, then you can relax. If not, then either start following these best practices to protect the reputation of your emails or switch to Pepipost and join the fastest growing good email senders community.

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