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Debunking email deliverability myths

We invited five industry leaders to join us at Email Camp 2023 to debate myths and rumors from the mysterious world of email deliverabiliy. In this post, the experts will investigate and pass their judgements – labelling these legends truth or myth once and for all.



There’s a ton of deliverability misinformation out there floating around in space. So much, that it’s often hard to know what’s a deliverability truth and what’s just a myth.  

So, to uncover the truth around some common deliverability misconceptions, we brought together a panel of industry experts to participate in our 2023 Email Camp conference and asked them to bust some of the biggest deliverability myths around. 

Read on our recap of Email Camp: Mission Control’s “The truth is out there: Debunking email deliverability myths” and discover the truth about IP and domain reputation, to open rates, and the depths of Gmail’s Promotions Tab. 

Email Camp 2023’s deliverability panel: The truth is out there 

Email deliverability is hard. It’s probably one of the hardest parts about email in general. That’s why we invited some of the biggest deliverability names in the industry – both at a brand and internet service provider (ISP) level – to discuss some of the most common email deliverability misconceptions

Want to meet our All-Star panel? Here are the experts:  

  • Alex Brotman, Sr Engineer, Anti-Abuse at Comcast 

  • Brad Gurley, Director of Deliverability at MessageGears 

  • Pankaj Kumar, Sr. Deliverability Analyst at Blueshift 

  • Tom Corbett, Email Deliverability Consultant at Iterable 

  • Kate Nowrouzi, VP of Deliverability at CPaaS at Sinch 

Check out what they had to say about avoiding spam filters and getting emails into the inbox by watching the full session below and check out our main insights below: 

Why is email deliverability so misunderstood?

Let’s start with a tough question, why is there so much misinformation and misunderstanding around deliverability?

Email deliverability is not only made of many pieces but is influenced by each individual sender’s needs, goals, and habits. What works for one might not work for all and because of that, there is a lot of misinformation floating around in the deliverability space.

Unfortunately, some of the myths out there – if you believe them – can have an asteroid sized impact on your reputation and deliverability, while others can really give you a boost. Since you can’t trust a myth at face value, we’ve dissected some of the most challenging ones.

Let’s dive in.

A new IP can be blocked during a migration

Migrations between IPs can be tricky.

Whenever you embark on a migration, there’s always going to be an adjustment period – kind of like getting a new roommate – where the mailbox providers may give you a bit of the cold shoulder as they get used to your new IP setup, learn its habits, and figure out what makes it tick.

The question is, do migrations automatically mean your new IPs will be blocked?

The panel’s ruling: True

This isn’t necessarily true or false all of the time but a blocked IP can be triggered by a migration.

However, you can mitigate blocks and manage your transition by keeping your overall reputation in mind and properly managing your domains and subdomains. If your domain is healthy and your former IPs had a good rep, the transition will be much smoother.

“If you have an established reputation for your domain or subdomain and are migrating to a new IP space, your migration can be successfully expedited with a lower risk of blocked IPs if you have a great reputation before you migrate.”

Kate Nowrouzi, VP of Deliverability for Sinch

If an ISP blocks your IP address just spin up a new one

When ISPs close a door, just open another one, right?

It’s easy to see why getting a new IP up and running might be a quick fix when you find that you’ve been blocked. But is this really the best way forward or are there unforeseen consequences to creating new IPs as needed?

The panel’s ruling: Myth

Spinning up new IPs is something a spammer would do to keep their scheme alive when ISPs shut them down.

Mistakes can happen where you might become blocked but it’s best to work with ISPs to resolve the issue rather than move to a different IP without addressing your sending practices.

“Not only is this a myth, spinning up new IPs is potentially extremely damaging. It is an action that makes you look like a malicious sender. Take time to analyze how you arrived at this point and make a plan to come out of your blocked state.”

Alex Brotman, Sr Engineer, Anti-Abuse at Comcast

Opens are a reliable metric

Senders are famously in search of a reliable metric that can be quickly referenced to paint an accurate picture of the success of a campaign. Some even believe that the open rate is a sort of email metric holy grail.

When it comes to getting the best insights into how your emails perform, is this metric the be-all and end-all?

The panel’s ruling: Truth-ish

We don’t want to outright say that open rates as a metric are dead, but that doesn’t mean they’re not reliable – just that you have to understand what an open rate is actually reporting on.

According to our panel, open rates have always been a rather unreliable metric to track user engagement, since they’re often inflated by automated clicks. When you look at your open rate, it’s important to also look for overall trends and compare other metrics, like click-through rates, to get the full picture.

If you can’t find a way to eliminate non-human interactions like automated clicks by virus software or browser extensions, then you’re going to have a hard time believing that your metrics reflect accurate open rates.

“Open rates are typically tracked through a pixel, and there are a lot of ways that an image can be loaded, such as through prefetching. This makes open metrics slightly less reliable on the user level in terms of knowing if users have opened a message, but open metrics are really valuable for quickly spotting trends like large increases or decreases in open rate.”

Brad Gurley, Director of Deliverability at MessageGears

A dedicated IP is always the best option to mitigate risk

If your send volume is extremely low, it can take a long time to build up a strong reputation. One way to expedite this timeline is to send on a shared IP. However, when you send on a shared IP you become subject to the reputation of the senders sharing that IP.

So, is a dedicated IP really the best way to address this?

The panel’s ruling: Mostly myth

This one is complicated, and the answer depends on what kind of sender you are.

There are a lot of situations where sharing an IP can be a great solution for a brand, and it can be hard to draw the line in the sand between “my send volume is low and I need a boost” (maybe a send volume of around 2000 emails per month) and “I send enough that a dedicated IP will protect my reputation.”

One helpful tip from our panel is to utilize subdomains to segment sending and safeguard your reputation. For example, the sending of transactional and promotional messaging would benefit from separate subdomains.

In terms of shared IPs, though, keep in mind that providers are looking at a combination of IP and domain reputation. So, even if you’re sending on a shared IP, your domain gives you some separation in terms of reputation from other senders.

"I always like to make the joke, if you ask ten deliverability experts how much volume you should send on dedicated IPs, you’re going to get eleven different answers. Everyone has their own methodology for what the cutoff is, what’s low enough volume where you can’t establish reputation vs when do you reach the high end where you need to start adding IPs."

Brad Gurley, Director of Deliverability at MessageGears

If your emails are going to the Promotions tab, Google will fix it for you

Perhaps the most mysterious entity in the vast universe of deliverability is Google itself.

This celestial giant operates within a shielded black box, and discovering its operational secrets has been a quest of email explorers practically since email began. Senders even whisper of a secret phone that you can use to call Google for a fix when things happen, like when your messages land in the Promotions tab but you want them in the primary inbox.

So, is there anything to it?

The panel’s ruling: Myth

The spam folder is not the Promotions Tab. The Promotions Tab is the inbox – we've covered this in detail in some of our deliverability content, but it’s often a misconception around senders. If your marketing messages are not going to the primary inbox, it’s because they don’t need to. Maybe you can contact Google, maybe you can’t – but if you find the secret phone, let us know.

The real issue is that Google is riddled with algorithms and machine learning specifically designed to support the best experience for the user. If the user moves a message between tabs, Google will likely respect it going forward – but they probably won’t grant your request as a sender to adjust your inbox placement.

“If a user is checking their Promotions tab, that means they have a very good buying intention. If your promotional email lands in the promotional tab, that’s the right place. Google has made the promotional tab for the user.”

Pankaj Kumar, Sr. Deliverability Analyst at Blueshift

In the future, domain reputation will be far more important

Most senders are moving towards prioritizing their domain reputation over their IP reputation with the belief that eventually domain reputation will be far more important. So, what did our panel have to say about this?

The panel’s ruling: Truth

IP reputation is sooo ten years ago.

While it’s still a factor, domain reputation is getting a lot more attention these days, as it is more tightly linked to your sender identity and is a more future-proof measurement of your reputation against updated IP versions.

And with domains taking the lead in the reputation race, subdomains become more and more important for reputation protection. If your promotional messages take a reputation hit, your transactional messaging or other streams are protected if they are on separate subdomains underneath your main parent domain.

“As we exhaust the IPv4 addresses available, people are moving into an IPv6 world. The IPs on each version may have different reputations but your domain will have the same reputation on both sets of IP systems.”

Alex Brotman, Sr Engineer, Anti-Abuse at Comcast

Less is more during the holiday sending season

Should you triple your send volume during the holiday season? After all, it’s also the peak buying season so why not increase your chances with as much messaging as possible?

We asked our panelists whether less was indeed more during the holiday season. Their answer may surprise you.

The panel’s ruling: Truth

Don’t send just for the sake of sending.

The holiday sending season keeps expanding so the advice that applies here is valid throughout the year. As an example, Sinch Email sent 45.7 billion emails in November 2023 alone, with a 16% surge in send volume for BFCM over the previous year.

Inbox fatigue is a problem particularly during peak sending seasons like Black Friday and Cyber Monday, but the inbox is crowded for more than those few days. Making your messaging more purposeful and more focused makes your sending more meaningful and more impactful.

“Year-round, my recommendation to marketers is to send less but personalize messages more. Email inboxes are massively crowded especially during the holidays. There is a person sitting behind each of the email addresses on your list, so take that into account.”

Kate Nowrouzi, VP of Deliverability at CPaaS at Sinch

You shouldn’t have too many subdomains

If subdomains are the magic ingredient to protecting your domain reputation, what is the limit to the number of subdomains you should create?

The panel’s ruling: Myth

There is no limit to subdomains in terms of best practices, but your subdomains should be purposeful and should make sense based on your sending. Basically, subdomains are for separating different types of traffic.

You’ll get the reputation ascribed to the highest-level domain that you’re sending from, probably your main parent domain. If you send three emails a year on a subdomain that won’t really make an impact, but if you’re sending all your emails on a single subdomain then that defeats the purpose of having one at all. 

“There is nothing negative about having too many subdomains. There is no magic number. If the volume on a subdomain is low enough it can confuse an IP filter. If you have recognizable traffic that has a specific purpose, then a subdomain makes sense.”

Kate Nowrouzi, VP of Deliverability at CPaaS at Sinch

DMARC setup is optional

DMARC can be difficult to set up and challenging for less technical senders to understand. There are some senders out there without the resources to make the change and implement DMARC and others who would have to cut through a lot of corporate red tape to get approval.

So, is DMARC necessary? After all, there are other – more straightforward – authentications out there.

The panel’s ruling: The times, they are a-changin'.

DMARC is a way of proving a sender is who they say they are, it helps to prevent spoofing and protects the inbox for recipients. While it is not a requirement for every mailbox provider out there, times are starting to change, and we predict it will be in the future.

In fact, senders who haven’t yet adopted it may not have a choice in the future if they want to be seen as a legitimate sender. Steps are being taken by mailbox providers Gmail and Yahoo in early 2024 that require bulk senders to adopt DMARC.

“It is optional technically, but it should be set up. I have seen situations where the subdomains have been spoofed because DMARC has not been set up. DMARC protects your identity.”

Pankaj Kumar, Sr. Deliverability Analyst at Blueshift

Changing ESPs will solve all your deliverability problems

“It’s not me, it’s my ESP.”

If this is your attitude, you’re not alone. There are senders out there who think that moving providers will solve their larger deliverability issues. It is true that not all ESPs are created equal, but is moving really the answer?

The panel’s ruling: Myth

This one is short and sweet. Your bad practices will follow you no matter where you go.

When choosing an ESP in the first place, don’t just partner with a provider for where you are in your email journey at that moment. Look at features that support things like scalability, reporting, and reputation and remember that ESPs prefer to partner with legitimate senders, and they will cut out any bad seeds that drag down other senders if they have to.

“If you’re forcing bad practices upon your ESP and your ESP disagrees with those practices, it doesn’t matter if you change ESPs since you’re taking those bad practices with you.”

Alex Brotman, Sr Engineer, Anti-Abuse at Comcast

Using “no reply” in the sender address is OK

If you’re using email to communicate with your customers in a variety of ways, it can seem practical for a sender to use a “no reply” address for certain communications depending on send volume.

After all, if you issue a mass update users can reply to, you’ll potentially have to field a large number of responses – and that is a tedious and time-consuming task.

Are there situations where a “no reply” address is recommended?

The panel’s ruling: Mostly myth

If you're sending a promotional or marketing email, a "no reply" address is definitely a no-no. If you're sending a triggered message about something like a shipping notification or a flight update, a reply address may not be something that could solve a problem for a user.

There’s some slight nuance to this myth depending on what type of message is being sent and what the purpose of that message is but you also have to consider that every message sent is an opportunity to build rapport with your recipients.

“We’re meant to be building relationships with our customers. “No reply” indicates that you don’t value their response.”

Tom Corbett, Email Deliverability Consultant at Iterable

Wrapping up

That’s a wrap! But if you think we’ve covered every deliverability myth out there then you are myth-taken (sorry, couldn’t help it). We’ve pulled out some of the biggest myths for this post but there’s more to explore and more deliverability best practices to uncover.

Check out the full panel discussion for more myths along with our other great Email Camp sessions in our Email Camp: Mission Control Youtube playlist. Or continue learning about email deliverability by checking out our best deliverability content.

Need help getting your email into the inbox? Get insights and recommendations with Mailgun Optimize or reach out to our team to discuss your email needs.  

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