So You Want to Send an Email: Best Practices to Ensure COVID Communications Get to Inboxes

By: Hileman Group  | 04/17/2020

Since the coronavirus outbreak began impacting businesses in the U.S., the volume of marketing emails went up substantially. The week of March 16 alone, HubSpot saw a 29% volume increase. And with a need for frequent updates to customers, patients or clients, this is the time to make sure your emails are getting where they need to be.

How can you ensure deliverability of your important COVID-19 communications? The enemy of successful delivery isn’t merely spam folders — it’s also bad list data, underreporting and less-than-best practices. So to help boost the safe delivery of your emails to inboxes when you’re sending at your highest volume, we prepared the following brief guide for navigating and improving your email send processes.

Deliverability Is Complex

Sending an email from point A to point B may sound simple, but many factors determine whether it reaches an inbox. The delivery of an email from your email service provider (ESP) platform (HubSpot, Marketo, Mailchimp, etc.) uses a sequence of over 15 steps. Only then is it delivered to your audience’s internet service provider or webmail provider.

There’s a principle in mechanics: the more moving parts something has, the more efficient it is but the more chance something can go wrong. Because email delivery isn’t as simple as A-to-B, email deliverability requires a certain set of best practices to help everything go right.

5 Best Practices for Strong Deliverability

Increasing and maintaining your deliverability takes work and should be part of your overall email marketing strategy. And many of the following practices go hand-in-hand with other best practices you might already use.

1. Ensure Valid Email Addresses

Your first line of defense to combat deliverability issues is your method for growing your subscriber audience. The best practice for acquiring valid email addresses is to use a double opt-in process. This requires the subscriber to confirm their email address by clicking on the link in a confirmation email sent once they sign up. Under a double opt-in methodology, a subscriber who doesn’t opt in through the confirmation email has not opted in at all.

You can include additional validation services to your email address collection forms. These include Bright Verify and Experian. They can help prevent invalid email addresses from being collected into your list and imported into your email platform.

2. Recruit the Recipient’s Help

Your subscribers can help deliverability when you provide “whitelisting” information. This instructs recipients to add the sending account to their email client’s list of “safe senders” or address book. Including these instructions on a subscription confirmation page can signal recipients to check their spam folder if they don’t receive an email. But including instructions or a link to whitelisting instructions in confirmation emails and the footer of ongoing emails can also help boost deliverability.

The other side of getting whitelisted, however, is staying whitelisted. To help avoid spam complaints later, be up-front and transparent when collecting subscriber email addresses about how frequently they can expect emails from you. Additionally, giving subscribers the ability to manage email preferences and particular subscription lists through your ESP platform may allow them to limit the frequency emails without unsubscribing from your sends entirely.

3. Throttle Your Sends

Each ISP or webmail service has different send limits — and even then, sending to your entire list at once could negatively impact your deliverability. While the importance of your message makes maximizing its distribution urgent, the simple solution may be “send throttling.” Send throttling limits the maximum number of outbound messages for a specified period. This can be done through delayed send throttling or rotating IP send throttling.

For delayed send throttling, we recommend limiting sends to approximately 20,000 emails for an individual list or population per 24 hours. With each daily segment you send to, monitor your delivery results. You may be able to slowly increase your send volume with each next segment, but continue to monitor deliverability.

In contrast, revolving IP send throttling spreads the entire send across several rotating IP addresses. This strategy is best for high-volume deployments, where daily send volume exceeds 50,000.

4. Keep Your Data Clean

ISP and webmail services provide feedback that impacts your deliverability. When your bounce rates or spam complaints are high or your general deliverability is low, that affects the reputation that services use to assess your trustworthiness as a sender.

We recommend using suppression features in your ESP platform to exclude inactive subscribers — for example, those who haven’t clicked on the last three emails. Additionally, you should remove any recipients who flag your email as spam. Continuing to send to these addresses may lead to blacklisting and poor sender reputation.

Additionally, efforts to reengage inactive subscribers can keep your data clean without winnowing down your list. Migrate inactive subscribers into a reengagement campaign using personalized content and marketing automation. Suppress recipients who fail to interact from future sends, but those who engage may reintegrate into regular sends — along with the benefit of new information you may have learned from their recent behavior.

5. Report Frequently

Pull email deliverability and engagement reports routinely based on your send frequency. If you send daily, assess your reports daily. Delivery rate is a clear indicator of successful practices.

When reporting, also consider these practices:

  • Segment soft or technical bounces by domain to see if a high proportion was blocked by any particular ISP or webmail provider. Throttle any future sends accordingly.
  • Monitor subscriber engagement to assess high-return versus ineffective content and sends. This should help inform your email strategy.
  • After each send, assess hard bounces and determine where those email addresses are coming from. Apply restrictions to those sources, such as additional verification steps.


Your emails require attention, and that means your deliverability and email send practices do as well. But by applying best practices to your data and your sends, you should be able to boost your success rates and get your communications where they need to be, when they need to get there.



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