You've designed a beautiful invitation for your event, polished the subject line, segmented your contact list, and clicked "send". Mission accomplished? Not quite.

According to a 2022 study by Campaign Monitor, the average open rate sits around 21.5%. Yet between sending an email and it actually reaching the inbox lies a factor that's often overlooked: deliverability.

It's one of the most powerful and underestimated levers of marketing performance.

In this article, we explain what deliverability is, what factors influence it, and above all, how to improve it in practice.

Definition of email deliverability

Deliverability refers to your email's ability to reach its recipient's inbox without being blocked by spam filters or rejected by servers.

Contrary to popular belief, clicking "send" doesn't mean the email has been received.

How is it calculated?

You can measure deliverability using a simple metric: the deliverability rate. It's calculated as follows:
Deliverability rate = (Number of emails delivered / Number of emails sent) x 100

For example, if you send 300 invitations and 288 arrive at their destination, your deliverability rate is 96%. A good rate is generally considered to be above 95%.

Difference with the open rate

You need to clearly distinguish between deliverability rate and open rate.

The deliverability rate indicates whether the email reached the inbox, while the open rate indicates whether the recipient opened the email.

Remember that you can't have a good open rate without first having good deliverability: it's the first condition for an effective email.

The delivery statuses you should know

An invitation-sending platform like Digitevent provides detailed delivery statuses that let you understand what happens after you click "Send":

  • Sending in progress: the message is on its way. It has left the platform but hasn't yet been accepted by the recipient's server.
  • Sent: the email has been accepted by the receiving server. It can now appear in the inbox, or in spam.
  • Delayed: the recipient's server is temporarily unavailable. Sending will be retried for 72 hours.
  • Opened / Clicked: the email was viewed or a link was clicked. These are signs of interaction confirming that the message was indeed delivered.
  • Dropped: the email wasn't sent because the address is known to be invalid.
  • Hard bounce: the email was rejected because the recipient's address is incorrect or no longer exists.

A high proportion of bounces or drops can, for example, explain a drop in your deliverability rate.

Keep in mind that analyzing the delivery statuses of your invitations is essential for assessing the quality of your contact database.

💬 Quote from the Digitevent expert:

"Deliverability is your emails' passport: without the right technical stamps and a solid reputation, your messages will never make it into the inbox." - Damien Remise, Account Manager at Digitevent

What factors influence email deliverability?

Deliverability doesn't depend on a single parameter, but on a combination of technical, behavioral, and contextual factors. Here are the 4 main ones:

Sender reputation: Your reputation is directly influenced by your sending practices. Every time you send an email, mail servers assess your behavior using several criteria:

  • The complaint rate: how many recipients mark your emails as spam?
  • The bounce rate: how many emails are returned due to an invalid address?
  • The engagement rate: are your emails opened, clicked, or deleted without being read?

Message content: tone, keywords, and formatting can trigger spam filters.

Technical configuration: to be properly identified as a trusted sender, your IT department must configure three key protocols that act as your emails' digital ID and play a central role in their credibility:

  • SPF (Sender Policy Framework), which verifies that the email was indeed sent from a server authorized by your domain.
  • DKIM (DomainKeys Identified Mail), which adds a digital signature guaranteeing that the message hasn't been altered.
  • DMARC, which orchestrates these two protocols and tells receiving servers what to do if authentication fails (let it through, quarantine it, or reject it).

Sending volume and frequency: sudden spikes or an excessive pace can be seen as suspicious.

Many factors affect your invitations' ability to reach their target. Fortunately, a few simple, concrete rules can significantly improve your deliverability rate.

Here, for example, are five symptoms that can help diagnose the health of your contact database, and act accordingly:

  • High bounce rate: signals an aging or poorly qualified database → clean up your database or revisit segmentation
  • Sudden drop in open rate: reveals a likely deliverability issue → analyze your content and check your SPF/DKIM protocols, with help from a technical expert if needed
  • Increase in unsubscribes: reflects an unsuitable message or too high a sending frequency → rework your editorial strategy
  • No interaction for 6 months: indicates dormant contacts, with a risk of permanent disengagement → launch a targeted re-engagement campaign
  • Lack of high-value content: pairs with the re-engagement campaign to recapture attention

8 best practices for improving the deliverability of your invitations

Understanding the factors behind email deliverability is good. Putting them into practice is better. Here are some simple, effective actions to boost the performance of your campaigns.

1. Regularly clean your contact database

Remember that a clean database is essential for maintaining a good sender reputation. Inactive, incorrect, or outdated addresses lead to sending errors or automatic drops.

To keep an effective contact database:

  • Check or remove contacts that have been inactive for more than 6 months.
  • Avoid purchased databases, or work only with trusted providers.
  • Use email address validation tools.

A high bounce rate is often a sign of an unqualified contact database. Over time, this can seriously harm your sender reputation, or even cause your domain name to be systematically flagged as spam.

Don't hesitate to use online tools like Kickbox to test the quality of your database.

2. Properly identify your domain

Mail services like Gmail or Outlook check whether your invitations are genuinely sent by you. Work with your IT department to make sure that your domain name is properly authenticated and that the SPF, DKIM, and DMARC protocols are correctly configured.

If most of your recipients belong to the same organization, involve that organization's IT department so it can recognize a specific IP address: this is whitelisting. This practice involves adding a sender or an IP to a trusted list, to prevent emails from being blocked.
Finally, make sure your sending address is consistent and professional.

3. Take care with the content of your invitations

The tone, style, and structure of your email directly affect whether it lands in the inbox, or in spam.

Spam filters analyze both the substance and the form of your emails:

  • Avoid overly salesy phrasing, the well-known "spam words": "Free!!!", Refunded, Gift, 100% Free, No fees, You've won!, etc.
  • Limit capital letters and exclamation points.
  • Keep an eye on the balance between images and text in your invitations.
  • Write content that's readable even without images.
  • Add personalization elements (first name, company, etc.).

4. Keep a good sending pace

If you send too many emails at once or too frequently, you can trigger alerts at mail providers. That's why you should:

  • Split up your sends to avoid traffic spikes.
  • Adopt a consistent frequency suited to your audience.
  • Avoid sending to thousands of recipients all at once.

Some servers delay or refuse sends deemed "sudden" or overly massive. Note that a good email-sending platform includes these practices by default in its features.

5. Always offer a simple way to unsubscribe

In accordance with the General Data Protection Regulation (GDPR), an unsubscribe link is mandatory.

Don't forget to place a visible link in the footer, and don't complicate the process (no multiple clicks, no proof required).

A user who can't easily unsubscribe is more likely to report your email as spam.

Making it easy to unsubscribe is a mark of trust, and therefore beneficial for your reputation.

6. Test your emails

A well-written email can still land in spam if it isn't tested properly.

Each mail service can interpret your email differently.

  • Send an email deliverability test to several providers (Gmail, Outlook, Yahoo, etc.).
  • Analyze the layout, readability, and inbox placement, whether on desktop or mobile, to ensure an optimal experience regardless of the device.

No need to worry: there are tools like Mail-tester to test your emails' deliverability.

7. Analyze the results and adjust

Statistics are your best allies for understanding and fixing what isn't working. Keep an eye on these metrics:

  • Delivery statuses (sent, in progress, delayed, etc.).
  • The deliverability rate (Number of emails delivered / Number of emails sent) x 100
  • The bounce rate (Number of undelivered emails / Number of emails sent) × 100.
  • The open rate (Number of emails opened / Number of emails delivered) × 100.
  • The click rate (Number of clicks on a link / Number of emails delivered) × 100.
  • Unsubscribes and spam complaints.

Quickly identifying anomalies lets you react before they affect your next campaigns.

8. Use a reliable sending platform

The solution you use to send your invitations plays an essential role in their deliverability. Not all platforms are equal: some apply strict rules to avoid blocks, others don't.

Choose a reliable invitation-sending platform like Digitevent, which includes technical best practices by default and lets you clearly analyze your campaign statistics.

As you can see, deliverability isn't just a technical matter: it's a genuine performance lever for your events. An undelivered invitation is a message that will never be read, one fewer attendee, and a missed opportunity.

Don't let your invitations fall into oblivion. Try Digitevent now to ensure your emails reach their targets, effortlessly.