Bulk email is a fantastic way to send information cheaply and fast, while adding personalised information. But when 85% of all email is spam, email service providers are increasingly looking for ways to reduce the amount of email spam being sent through their gateway – because just one rogue sender can cause hundreds of legitimate senders to have their messages blocked or delayed.

So if you’re wondering:

  • Why was my email dropped?
  • What does it mean when email bounces?
  • Why does it look like my email was delivered, but the recipient can’t see it?

It could be that your message was flagged for spam – even if it wasn’t spam.

So what happened?

There are 5 email events that can happen when you send an email via our SMTP gateway. You’ll find that most email providers have the same or similar names for these events.

So what exactly does it mean when emails are delivered, dropped, deferred, processing or when the email bounces? Read on for your guide to email deliverability and find out how to ensure that your next email campaign reaches the right inbox.

Deferred, bounced and dropped emails – when email misses the mark

email events

When you send a email, that message goes through a series of complex processes to reach the recipient – all within seconds. To send a basic email, you will often use an email client like Outlook, Gmail, Yahoo Mail, Hotmail, etc. Once you have composed your message and clicked send, the email is sent to your email client’s server. The server then finds out which server to send the email to and relays it to the recipient server. The server then (hopefully!) delivers this message to the email client of the recipient.

When sending email in bulk, it’s more complicated. Personal-use email clients like Gmail, Outlook, etc are not equipped to handle high email volumes from businesses; this is why you will need to use an email platform for sending at scale.

Once sent, the email can return one of the following statuses.

  • Delivered – your email has been delivered to the receiving server.
  • Processed – essentially a ‘completed’ status on our end; your message is good to go.
  • Dropped – generally this is when an email is stopped from our end. There are several reasons why we would drop an email, read on to find out more.
  • Deferred – the receiving email server has delayed delivery of the message.
  • Bounce – the receiving email server has refused delivery of the message.


It’s common for email marketers to expect a ‘delivered’ status to mean that an email message has reached the inbox of the recipient. However, this status simply means that the email has been delivered to recipient server, not necessarily to recipient’s inbox. From there, the server has the option of delivering the message to the recipient’s inbox or sending it to the junk/spam folder. On the rare occasion, the email server can choose to delete or ‘drop’ the email, meaning it is not even visible in the spam/junk folders.

When the receiving server makes these decisions, they are purely based on the reputation of the sending server and the email content. Senders that have cultivated a ‘spammy’ reputation (through receiving high numbers of spam complaints) or are sending content that raises red flags about the propensity to generate spam complaints, are less likely to reach the email inbox of the recipient.


This is a temporary state while we prepare to send the message. Generally most messages will be at the processed status for a minute or two, if not less. It’s simply what happens when a new email job is created, the message has been received by us and is ready for sending.


A dropped email event can occur when an email platform identifies spammy content and removes the offending message before it reaches the recipient server, to protect sender reputation. There are other reasons that an email might be dropped by ClickSend, including when a subscriber has already unsubscribed or bounced previously, invalid SMTPAPI header or recipient list over package quota.


There are several reasons why an email might be met with a deferred status. A deferral is where the email is temporarily unable to be delivered. The most common reason for this is that the receiving email server has seen high volumes of emails in a short amount of time and suspects that the sender could be spammy. By deferring, or throttling, the emails the receiving server can prevent email inundation while investigating whether these messages are spam. Other reasons that the email may be deferred is that the recipient mailbox may have reached capacity or technical issues with the receiving server. When this occurs, we attempt to send the message for up to 72 hours, before it becomes a soft bounce.


When an email bounces, it means that it was unable to be delivered. There are many reasons why an email might bounce; these can be categorised into hard bounces and soft bounces. Hard bounces are when emails cannot be delivered for permanent reasons: the email address does not exist or is incorrect. Soft bounces occur when a mailbox might be full or server offline – while attempting to deliver, these messages they will have a status of deferred, until 72 hours have passed and the email has not been delivered. A soft bounce may also be given a status of ‘blocked’ on some email platforms.

It’s important to ensure your bounce rate (especially hard bounces) remains low to maintain your sender reputation and ability to send bulk emails.

Why did my email not get delivered?

why are my emails not being delivered

There are a number of different reasons why emails might get dropped, blocked or result in a bounce. Here are some of the most common reasons we see.

Sender Reputation

Your reputation as an email sender is a massive factor for email deliverability; that’s why it’s so important to protect your sending reputation. It also is affected by the content you send and to whom you send it.

Sender reputation is heavily based on the reputation of the IP address you are sending email from, plus that of the sending domain. When sending through an email platform, businesses that send low volumes may be using a shared IP address. This means that these companies share the same sender reputation with other businesses on the IP address. Meaning that if one sender gets caught sending spam, all users of the IP address are likely to take a hit. Because of this, reputable email platforms are continually looking for ways to prevent spammy messages from leaving their gateway.

If you send a lot of email, it may be worthwhile to use a dedicated IP address for full reputation control. Or if you are sending transactional and marketing email, we do recommend that you use two different IP addresses for them. Marketing messages tend to be watched more closely than transactional messages, so if you’re a new sender and you haven’t warmed your IP address, a new email marketing campaign may end up throttling your regular transactional messaging.

Email Content

If you are seeing high levels of dropped, deferred or bounced messages – and think your reputation has taken a hit – it might be time to look at your email content and contact list. One of the first places to start is to take a step back and see whether the messages you are sending could be considered spammy.

Here are a few red flags when sending email:

  • Using free URL shorteners like bit.ly and ow.ly – these are frequently used by spammers to conceal their true identity.
  • Asking readers to verify their identity – any message that sounds like a request for personal information could easily be a phishing attempt.
  • Using a different email domain as your sender.

For example, if Jeff signed up to an account with ClickSend as jeff@bird.com and attempts to send email from a domain other than bird.com, he’s likely to be flagged as spam.

  • Excessive formatting and incorrect spelling.
  • Bad code – poorly written HTML can cause emails to be flagged if spam filters are unable to parse the code.
  • Keyword stuffing, pushy sales tactics – good emails are about creating useful and engaging content. If a message does not add value to your contacts, subscribers are likely to opt out, or worse, report spam.

List Hygiene

List hygiene is very important for keeping your bounce rate down and thus maintaining your sender reputation. If you’re seeing a high rate of hard bounces, it could be that the email addresses are incorrect or no longer valid.

Think about the last time you cleaned your contact list…

  • Do you remember when this was, if ever?
  • Do you use a double opt in for your contacts to subscribe?

💡Contact list need a cleanup? Head over to our list cleaning tips for more information.

Invalid Email Addresses

One of the most common reasons an email will bounce is because the email address is invalid. This could be due to a subscriber including a typo in their email address or a staff member entering an incorrect email address into your database. Whatever the reason, just like with snail mail, the message won’t find the intended recipient if the address is incorrect. Ensure that the emails on your subscriber list reach their intended recipient by enabling double opt-in. This is where subscribers are sent an email confirming their permission to be emailed, or even sent to a ‘preference centre’ to choose which type of emails they would like to receive from you. Once the user has double opted in, you can be confident that the email address is correct and belongs to the expected recipient.

List Quality Control

It goes without saying, buying email contact lists or email address harvesting are simply no-go. Not only is email address harvesting illegal, you will inflict damage on your sender reputation that will take a very long time to rebuild. These people are not likely to be interested in your product or service as the people who actively subscribe to your database or have had a previous interaction with your business. Furthermore, some email providers put out email addresses to be harvested and sold on lists purely to catch out those senders who engage in shady contact list building – land in one of these spam traps and you may find yourself unable to send email.

When you add contacts to an email list, there will always be a degree of contact deterioration. People may change their work and no longer use their former work email address, change to another provider or simply stop checking certain accounts. Regularly clearing out unused email addresses will help to maintain the health of your email contact list.

But what about those who are simply not opening your emails? Periodically you should run a re-engagement campaign in order to weed out the contacts that are simply uninterested and are never likely to open an email from you.

With a clean contact list, not only should your email deliverability improve you should see greater email engagement.

Looking to send transactional email that gets delivered? Choose an email platform that puts deliverability at the forefront. Sign up for your free trial now.