How to Build a Scalable Email Campaign Without Sacrificing Deliverability

A few years ago I was in charge of the email marketing for a skincare company that had just crossed 40,000 subscribers. Everyone was ecstatic - the founder wanted to send daily promotions because more emails = more sales. Makes sense, until day 16 when our open rates dropped 5x and Gmail began filing us in the promotion tab, and subsequently, the spam folder. This was my first painful lesson that growth and deliverability are not the same, and that pursuing the former without the latter will eventually hurt both.

This is the lesson all email marketers need to internalize from day 1 - you can have the most engaging creative, the perfect subject line, and sell the best products known to man, but if you're not sending the emails in a way that internet service providers will allow them to be seen, all of your effort will be wasted.

Start With the Boring Stuff: Your Sending Infrastructure

Before even thinking about engaging subscribers via email, I highly recommend taking a step back and setting up your SPF, DKIM, and DMARC records. I know, I know it's not exciting, but I promise you that doing so will save you untold amounts of pain and suffering in the long run. When I began working with that skincare company they were sending emails from their main domain, but after doing an audit it turned out that their DKIM signature was misconfigured (and had been for some time).

Create a subdomain for your marketing emails instead of sending them from your primary one.

That way, if your marketing emails' IP address gets blacklisted your customers' transactional emails (password resets, order confirmations, etc.) won't be effected as those are sent from a different address. You'll also notice that those inboxes are much less likely to mark your transactional emails as spam since they appear in their promotion tab. In fact, one company cut their unsubscribe rate in half by using a separate sending domain for transactional and marketing emails as customers who would normally spam the complain button with the marketing ones now began to associate the transactional ones with an actual person.

Warm Up Before You Scale Up

One of the first mistakes I made in my email marketing career was warm up. A B2B SaaS company wanted to change ESPs and move from MailChimp to a dedicated ip address. I assumed, incorrectly, that the best way to do so was to begin sending to the 90,000+ contacts they had with the new address as soon as MailChimp was shut down. In reality, mailbox providers have algorithms in place to prevent new ips from spewing hundreds of thousands of emails at once.

This is especially true for Gmail and Outlook who throttle ips that have little or no history with them.

We had to slowly begin warming the ip by sending to the most engaged 500 contacts (subscribers who had opened or clicked on any emails from us in the last 30 days) and then gradually increasing the send volume by about 20-30% every 2-3 days. This allowed us to hit a healthy 94% inbox placement rate (according to GlockApps) by day 25 and fully launch the campaign. By comparison, another brand we worked with didn't warm up their IP address at all, resulting in only 61% inbox placement for their first few thousand emails. I know it wasn't the most exciting thing to have to wait two and a half weeks before hitting the send button, but had we not done so it's likely their inbox placement would've been even lower.

Segmentation Is Not Optional, It's Survival

A furniture retailer I worked with was sending one email to their entire list every Tuesday and Friday, no matter who opened or didn't open their emails. Engagement was low and so was their inbox placement, but what really hurt was their IP reputation as it plummeted alongside their engagement rate.

We recommended splitting them into the obvious three categories: active buyers (purchased within the last 90 days), browsers (viewed items online but haven't purchased yet) and dormant customers (have not purchased or browsed any items online within the last 6 months). The dormant group was then put onto a re-engagement campaign which consisted of nothing more than two emails asking if they still wanted to receive emails from us. With no response after those two emails, we opted to move them to the suppression list (don't send them emails anymore) as it was clear that no amount of prompting would convince them to begin engaging with us.

It took a little getting used to but after a few weeks their open rates improved by almost 9% (from ~18% to nearly 27%) not because they suddenly were interested in buying more furniture, but rather because we stopped having to spam those who were never going to reply.

Frequency Should Match Behavior, Not Ambition

Ecommerce and SaaS marketers especially can feel the pressure to send, send, and send again as there's always something to promote - a flash sale, a limited time offer, an upcoming feature release, etc. Unfortunately, constant high volume spamming will eventually get you throttled by mailbox providers as no matter how good your content is your email volume needs to match your recipient's expectation of how often they should receive them.

The best way of determining this is to look at engagement rate on a per person basis and create rules within your email service provider that allow you to send more frequently to people who've shown higher levels of engagement (opened or clicked on your emails more often in the last 30/60/90 days) and less frequently to those who aren't as interested.

With one fitness apparel brand we told we wanted to send to our customers more often (up to 4 times per week) but didn't want to overwhelm those who only wanted to hear from us a couple times per month, we created a rule that segmented recipients based on how many emails they'd opened in the last 30 days.

Those who opened 3 or more emails in that period were added to our high frequency sending list while those that hadn't opened any in 45 days were moved to a low frequency list with lighter content and more spaced out subject lines. No one really talks about the rules inside your email marketing platform, but they're vital in ensuring that those who want to hear from you can without hurting those who don't want to hear from you as much.

Content Still Matters, Even for a Technical Problem

Even though the technical aspects of email marketing are arguably more important than the content itself, I want to acknowledge the importance of good content, especially when it comes to your subject lines and the ratio of text to image in any email you send.

Spam filters have gotten much more sophisticated in the past few years and will now penalize messages with too many exclamation points, all caps, words like "free" or "urgent", and image-heavy text. There are plenty of other spam indicators that can hurt your deliverability as well, but you want to especially keep an eye out for the aforementioned image/text ratio as some mailbox providers will automatically flag anything where the text is buried inside an image.

I was actually surprised to learn that plain-text-style emails did better in certain cases for one non-profit I worked for. Their donor renewal campaign that was sent as a simple text email (which looked like it was sent from an actual person) had a 41% open rate compared to 22% for their more traditionally-designed template. It was surprising, but the more casual feel and lack of corporate branding was far more engaging for certain recipients who felt that the standard donor newsletter was just too formal for them. This may not apply in all cases and there are certainly some things to be said about good design, but you don't always have to go full HTML to get good replies.

Monitor Like You Mean It

This final tip may come across as a bit of a cop-out, but you need to be constantly aware of what's happening with your marketing emails as deliverability really is a constant process rather than one-time task. I personally look at Google Postmaster Tools every week or so for any of my clients that are sending significant volume via Gmail. This tool allows you to see spam rates as reported directly by Google, along with domain and IP reputation. It's a much more accurate indication of where your emails are actually going than anything your ESP of choice might offer. As a rule of thumb, spam complaints should remain below 0.1% on average, and if they're rising above that I immediately investigate if there have been any recent changes to the campaign or list.

I also highly recommend using seed lists to test how your emails are being received before sending to the larger audience.

By putting together a few simple test emails and sending them to a few different inboxes (Gmail, Outlook, Yahoo, and a couple smaller services), you can get a good idea of how most of your recipients will receive a particular campaign, allowing you to address any potential deliverability issues before they become bigger ones. It may seem tedious, but in my experience it takes no longer than 15 minutes per campaign and has saved me numerous headaches by highlighting potential deliverability issues in advance.

What I Would Tell Someone Starting This Today

If I were to begin the email marketing process all over again, the first thing I would do is double check that my SPF, DKIM, and DMARC records are all set up correctly before sending out a single email. It's also important to remember that list growth and subscriber volume should be a measured process rather than something that happens all at once.

Those companies with the best deliverability rates across all sectors are also the ones that have the most patience at the beginning when building their list. Deliverability management is something that should be built on slowly, carefully, and deliberately over time. It's not something that is turned on or off, but rather nurtured like any long term relationship.