Best practices for maintaining strong email deliverability

Follow these best practices to ensure that you have strong email deliverability metrics

Maintaining strong email deliverability to all of your contacts, including those provided by Opensend,  is important to having a strong reputation with mailbox providers and ensuring that your emails land in the inbox instead of the spam folder. In this article, we'll cover important considerations when emailing Opensend-identified visitors, and some general best practices.

Considerations when getting started with Opensend

Before you start emailing Opensend-identified visitors, ensure that your sending domain has a strong email reputation - unless the emails you send are landing in the inbox, they won't do you any good! Check deliverability metrics in both your email provider (i.e. Klaviyo, Iterable, etc.) and in Google Postmaster Tools to ensure that your reputation is strong and that you have good open rates. For more robust monitoring across inboxes, consider a monitoring tool like MxToolbox. If your deliverability is poor, follow the best practices below to warm up your domain.

Assuming your domain is warmed up with a good reputation, your ready to start emailing Opensend-identified visitors, with the following considerations in mind:

  • Be mindful of any sharp increases to your overall email volume. If the daily volume of Opensend-identified visitors is high relative to the average daily email volume from your domain (i.e. >10%), you should slowly increase the volume of visitors receiving the welcome flow (i.e. start by sending the welcome flow to a subset of Opensend-identified visitors - in the meantime, you can engage all identified visitors who trigger abandonment flows and via non-email channels, such as via our Facebook Integration).
  • As you ramp up, continuing monitoring your overall reputation and spam rate. Inbox providers like Google require that your overall average spam rate is less than 0.3%, and ideally less than 0.1%, so monitor that in Google Postmaster Tools and/or monitoring tools like MxToolbox.  Keep in mind that the important metric is the overall spam rate for your domain, not for one specific email or flow. The first couple of emails in your Welcome flow will likely have the highest spam rate of any Opensend-related emails (if the occasional visitor is unhappy about receiving an email from you, they'll likely mark it as spam right away), and that's ok...as long as your overall spam rate remains within the guidelines.
    • Example: If your email domain sends, on average, 10,000 emails per day to your existing list, new purchasers, subscribers, etc. with a spam rate of 0.05%, and an additional 500 initial welcome emails with a spam rate of 0.4%, your overall spam rate is 0.07% - well within the limits even though one email in your flow is higher than the limit.

If you do see any potential issues:

  • First, ensure you that your are following general deliverability best practices and welcome flow best practices.
  • Next, increase the percentage of emails you send to highly engaged visitors while decreasing the percentage to less engaged. Be sure that you are segmenting profiles in your email marketing system and prioritizing those who have engaged recently in your ongoing campaigns (i.e. engaged profiles should receive emails more frequently than unengaged profiles).
  • If necessary, consider lowering the number of Opensend-identified visitors that are getting the welcome email flow to ensure that it's under 10% of your total volume. The first welcome email is the coldest Opensend-related email that you send. In your email platform, add a branch to the welcome flow and have a certain percentage of the visitors receive nothing. You can still retarget those skipped visitors with Facebook ads, via our Facebook integration, with postal retargeting, and include them in big campaign blasts, but it will lower the volume of the coldest emails as a percentage of the total. A/B test various content and timing to hone in on an approach that minimizes the spam rate - once you've optimized your flow, you can ramp the volume back up.
  • If still concerned, reach out to our support team or your customer success manager to discuss increasing the thresholds before which Opensend identifies a visitors on your site. This will decrease the volume of emails and limit the remaining to the most engaged visitors.

General Best Practices

Here are some general best practices to make sure your emails reach your contacts:

  1. Use a professional domain: Use a custom subdomain associated with your business or organization. A custom domain lends credibility to your emails.

    A branded sending domain allows you to send emails that appear to be coming from your brand and allows you to have better overall control of your sender reputation. If you don't use a custom domain, the sender information at the top of an email message will show its coming from your email marketing platform  (i.e., “sent on behalf of '' or “via klaviyomail.com”).
  2. Authenticate your domain: Implement SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail), and DMARC (Domain-based Message Authentication, Reporting, and Conformance) records to authenticate your domain. This helps prevent your emails from being flagged as spam.

  3. Warm-up your domain: Gradually increase the volume of emails you send from your domain to build a positive sender reputation. Start with a small number of emails and gradually increase the volume over time. Warming is the period of time in which you are establishing a reputation as a legitimate or “good” email sender. There are tools available which can be used to warmup your email sender in an automated way, hence we suggest utilizing an email sender warmup platform.

  4. Maintain a clean list: Regularly clean your email list by removing invalid or bounced email addresses. High bounce rates can negatively impact your sender reputation. Use the Opensend Revive service to provide up-to-date email addresses for your subscribers where the existing email in your system has started bouncing / become undeliverable.

  5. Avoid spam words: Avoid generic or spammy-sounding email subject lines and content. There are a number of "Email spam test" tools available which can be utilized to check for common spam words in your email content.

  6. Clearly identify yourself: Make sure your sender name and email address clearly identify who you are and the purpose of the email. Avoid misleading or deceptive sender information.

  7. Provide an unsubscribe option: Include a clear and easy-to-find unsubscribe link in your emails to give recipients the option to opt out. This is not only a best practice but also a legal requirement in many jurisdictions.

  8. Send high-quality content: Ensure that the content of your email flows is relevant and valuable to the recipients. Low engagement rates can negatively impact your reputation.

  9. Manage email frequency: Avoid sending too many emails to the same recipients in a short period. Space out your email campaigns to prevent recipients from flagging your emails as spam. You can find more details on Opensend suggested best practices to engage with contacts here.

  10. Test and optimize: Continuously test different elements of your email flows, such as subject lines, and content to determine what resonates best with your audience and improves open and response rates.

Here are the detailed guidelines on email deliverability improvement from a few of the platforms Opensend Integrates with; if you use another provider they likely have similar guidelines:


Remember that the success of email flows to Opensend contacts not only depends on the sender email setup but also on the quality of your messaging and targeting. Always aim to provide value to your recipients and build a positive reputation over time. 

If you are following all the best practices and still running into issues like high spam rates, please contact your Opensend customer success manager or submit a ticket with our support team here. We can review your setup and Opensend configuration for potential optimizations to increase your deliverability rates.