Email Events: Delivered, Bounced, Blocked, and Deferred — what do they all mean?

Bulk email is a great tool for notifying staff, clients, suppliers or other stakeholders of important information or for sending promotional material. It’s cheap, near-instantaneous, can be automated and personalised. However, email is only effective to get your message out there if your recipients are receiving, opening and engaging with your message. The first step to maximising your email reach is to understand your email events and how your numbers stack up. This may be very different depending on the nature of the messages being sent; transactional emails tend to pull better engagement events than promotional or marketing messages.

Find out more about transactional vs marketing email.

There are nine main email events that are fired when an email campaign is sent through ClickSend. Read on to find out more and how to use these stats to amp up your email marketing campaigns.

Sending an Email: Email Delivery Events

When you click send on any single email, that email goes through a series of complex processes to reach the recipient and these processes occur in minutes, if not 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, more often than not, delivers this message to the email client of the recipient.

When sending mass email, it is all the more complicated. Personal use email clients like those listed above are not equipped to handle high email volumes from businesses; this is why you will need to use an email platform to send bulk email. Also, email platforms will generally have ready to use email templates to ensure that your business messaging looks slick and on-brand.

When you send an email through ClickSend, there are a few different email events that can be attained:

  • 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 Are My Messages Not Being Delivered?

Your reputation as an email sender is a huge contributor to your email deliverability; that’s why it’s imperative to protect your email sending reputation. It also is affected by the content you send and to whom you send it.

Sender Reputation

Sender reputation is heavily based on the reputation of the IP address you are sending email from as well as the reputation of the sending domain. When sending through an email platform, businesses that send smaller email volume may be sending through a shared IP address. This means that these companies share the same sender reputation with other businesses on the IP address. Given the potential for one bad player to affect the deliverability of other businesses, reputable email platforms tend to carefully monitor emails from companies to ensure they adhere to best practices.

For companies that send large email volumes, 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. Otherwise, if you have not warned your IP address, you may find that by sending a massive marketing campaign your encounter deliverability issues for your important transactional communications.

If you think your reputation may have taken a hit, you should consider the content that you are sending and who you are sending it to.

Email Content

If you are seeing high levels of dropped, deferred or bounced messages it might be time to investigate your emails. One of the first places to start is to take a step back and see whether the messages you are sending could be construed as spammy.

There are plenty of reasons why an email may appear like spam, including but not limited to:

  • Using free URL shorteners like and — these are frequently used by spammers to conceal their true identity.
  • Text asking readers to verify their identity — any text that sounds like a request for personal information can be construed as a phishing attempt.
  • Using a different email domain as your sender.

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

  • Excessive formatting and incorrect spelling
  • Bad code — badly written HTML can cause emails to be flagged as spammy 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 value-add, 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?

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.

Email Re-engagement Campaign Examples

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

Receiving an Email: Engagement Email Events

So your email has been delivered… what’s next?

Great! Your beautifully crafted email has reached the mailboxes of your subscribers. Watch on your email platform dashboard as your engagement events gain data in real time. Especially useful to analyse are:

  • Opens — how many people opened your email
  • Clicks — how many people clicked on your email
  • Unsubscribes — the number of people who have unsubscribed from further messages from you
  • Spam Reports — those who have clicked ‘report spam’ in their email client


Once an email is opened and the images load, this will fire off an ‘opened’ email event. Since email opens are tracked by a small transparent image beacon, images need to be downloaded in a message before an open event can be fired. This is the only way that email platforms are able to track opens on emails. Open rate is simply calculated as:

Open Rate = Number of Emails Opened ÷ Number of Emails Delivered

Open rate is an important metric to note and is affected by the quality of your subject line, email timing, from name. Improve your open rates through:

  • Segmenting your contact list and tailoring your subject lines for different groups
  • Personalising your subject lines
  • Sending at the optimal time and day to maximise open rates (bearing in mind that your subscribers may be in different time zones)
  • Consider having the sender email look like a human, rather than your business name or marketing team.

Use A/B or split test to get data on what subject lines, timing and sender names work best for your audience. This will help you maximise your email open rate.


Clicks are affected by the quality of the content in the email: how much the content resonates with your audience, how strong your call to action is, etc.

Many in the industry place importance on maximising your clickthrough rate (CTR). You can work out your CTR as:

CTR = Number of Clicks ÷ Number of Emails Delivered

However, a metric we find more useful for determining your email content quality is the click-to-open rate (CTOR). This is a ratio of the number of clicks compared to the number of emails that were opened:

CTOR = Number of Clicks ÷ Number of Emails Opened

Since clicks are an action people take upon engaging with the content in the email, focusing only on the subscribers who opened the email when looking at who clicked is far more logical than all recipients.

So how can you maximise your number of click events from the customers who opened your email?

  • Understand your customers and what they want: are you alleviating a pain point or value adding with your message?
  • Ensure the email is easy to read/scan over: people don’t read email the same way they’d read a news article or blog post. Make it succinct and easy to digest, with the most important information above the fold.
  • Include a strong call to action.
  • Use strong visuals to entice readers to click
  • Make it as easy as possible to click — ensure links are clearly clickable and have enough space to click on mobiles.

Don’t forget to:

  • test your email template on different devices to ensure your content appears as expected when it reaches mailboxes.
  • conduct split tests in order to find out what content resonates with your audience.

When conducting split tests, ensure you are only changing one test variable so that you can draw strong conclusions for tests.


It is important that if you are sending marketing messages, you offer subscribers a way to opt out or unsubscribe from your emails. In most jurisdictions, it is illegal to send commercial email without a way to opt out — see Spam Act 2003 (Australia), CAN-SPAM (US), GDPR (Europe), CASL (Canada), etc.

While unsubscribes seem like a nuisance to many senders, they are of critical importance to monitor. Not just because it is important to stay on top of managing unsubscribes (or use an email platform that looks after them for you), but because of what the number of unsubscribes might tell you. If you notice a spike in unsubscribes following an email campaign being sent, this could be a strong indicator that your content missed the mark.

Spam Reports

You know you’re in trouble when your subscribers report you as spam. Note spam reports differ from unsubscribes; if subscribers click ‘report spam’ instead of unsubscribe, chances are that they are already somewhat frustrated. This sends a report back to their email provider, which loops it back to the sender email client. These can often happen if unsubscribe requests are ignored and are dangerous to you as the email sender, as it can be damaging to your sender reputation.

Understanding email events and their associated data is the first step in understanding how well your email campaigns are performing and how to drive the most value out of them.

Don’t just entrust your email campaigns to any provider; choose an email platform that puts deliverability at the forefront. Sign up for your free trial now.




Business Communications. Solved. Otherwise a massive lover of all things tech and marketing.

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Business Communications. Solved. Otherwise a massive lover of all things tech and marketing.

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