How Zelo Works to Optimize Email Deliverability

Email deliverability refers to the ability of an email message to reach the intended recipient's inbox. It is a critical aspect of email marketing and internal communication, as a low deliverability rate can result in a significant loss of potential engagement and information. Many factors can affect the deliverability of an email, including the sending IP, the sending domain, the email content, and the recipient's email provider.

Written by

Simen Ytre-Arne

January 4, 2023

Sending IP

One crucial factor that can impact email deliverability is the sending IP. Internet service providers (ISPs) use IP addresses to identify the source of an email message. If an IP has a history of sending spam or malicious emails, it is likelier to have a low deliverability rate. On the other hand, an IP with a good reputation is more likely to have a high deliverability rate. To improve the deliverability of an email, it is vital to use a dedicated IP or a shared IP with a good reputation.

How Zelo deals with sending IPs

Zelo has a dedicated IP address for sending emails, which provides several benefits.

  • Zelo monitors that the platform is accessed only by serious actors sending legit content to appropriate audiences that don’t harm the IP’s reputation.
  • Customers can allow-list the dedicated IP address to ensure messages from Zelo are not blocked by internal tools and firewalls.
  • On request, Zelo can also facilitate dedicated IP addresses per customer.

Sender Domain

The sending domain is another factor that can impact email deliverability. A domain with a good reputation is more likely to have a higher deliverability rate. To improve the deliverability of an email, it is essential to use a domain with a good reputation and to check the domain's sending reputation regularly.

How Zelo deals with sender domains

By default, emails sent from Zelo are sent from the domain. A customer can customize the sender name and reply-to address. However, we do not recommend using the default domain for larger audiences as other senders might impact the reputation.

Instead, Zelo allows customers to configure their account to send from a custom domain they control. This way, the customer has complete control over their reputation and allow-listing. Adding three CNAME records to your DNS is necessary to complete the domain setup.

Email Content

The content of an email can also affect its deliverability. Emails containing spammy or malicious content are more likely to be flagged as spam by ISPs, which can result in low deliverability. To improve the deliverability of an email, it is essential to avoid spammy words and phrases, use a clear and concise subject line, and ensure that the email content is relevant and valuable to the recipient.

How Zelo deals with email content

It is, of course, the customer who decides and designs the content of an email or message, and Zelo does not scan or monitor the customer’s content in any way. However, the use case for Zelo as an internal comms tool rarely meets the need of sending commercial or malicious emails, meaning email content is seldom seen as a deliverability issue.

Zelo’s email builder is optimized to comply with the latest HTML standards from the most prominent email providers like Outlook, Google, Yahoo, etc., which lowers the chance of content filtering.

Recipient’s Email Provider

The recipient's email provider is another factor that can impact email deliverability. Some email providers have stricter spam filters than others, which can result in a lower deliverability rate for emails sent to those providers. To improve the deliverability of an email, it is essential to follow the guidelines of the recipient's email provider and to test the email across different providers to ensure that it is delivered as intended.

How Zelo deals with different email providers

This is one area of deliverability where Zelo can’t optimize or tweak the settings for every occasion. Allow-listing the sending IP address and sender domain is crucial to avoid an email provider’s spam filters.


In conclusion, email deliverability is essential to email marketing and communication. By allow-listing the sending IP and sending domain, and crafting quality content, you should have no problems reaching the intended recipient's inbox.

You can always contact the Zelo team for any questions or assistance to configure your account properly.

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