Ask the Expert: Sridhar Chandran, Senior Deliverability Consultant

July 26, 2022
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Opinions expressed by Twilio contributors are their own

Ask the Expert: Sridhar Chandran, Senior Deliverability Consultant

Countless myths abound in the world of email deliverability. That’s why there’s no one better to clear up these common misconceptions than the leading experts in the world of email. Every month, we’ll bring you a Q&A with leaders from inbox providers, spam trap networks, antispam systems, and more in our new Expert Series blog. 

In our first Expert Series blog, we’re chatting with Sridhar Chandran. Sridhar is a Senior Deliverability Consultant at Twilio SendGrid with an incredibly unique and extensive background in the world of email. With over 14 years of experience working in email and antispam, Sridhar started his career as a postmaster at AOL, where he spent over a decade preventing email abuse and helping legitimate mailers get to the inbox. He hopes to bridge the gap between senders and receivers by helping define the next generation of email policies and deliverability best practices.

Now, let’s dive in.

7 questions with deliverability consultant Sridhar Chandran

1. What’s the most common misconception marketers have about how ISPs receive and interpret signals?

There are quite a few misconceptions among marketers about how receivers filter emails, but the primary one is that “one” signal alone can cause a block in your mailing. 

Marketers tend to chase blocklists and spam traps, but all these in isolation don’t cause blocks. Yes, being blocked or hitting a spam trap could indicate a systemic issue, but it’s not what causes an inbox service provider (ISP), like Yahoo! or Gmail, to block your emails.  

Equally importantly, most ISPs build and/or utilize filters using customer engagement data and complex machine learning to determine mail placement. As a result, any deliverability issues that senders experience are unique to the ISP and often span a wide range of factors.

2. In the wake of Apple’s MPP, marketers need to focus on negative signals. Can you clarify what exactly that means from an ISP perspective? 

Open rate has been a key performance indicator for marketers for a long time—until Apple’s Mail Privacy Protection or MPP came and spoiled the party. But most receivers always placed this below This Is Spam (TIS) and This Is Not Spam (TINS) reports.

You can find it via the Report spam button or what we call TIS reports, as the TIS and TINS have the most significant effect on reputation systems. 

Additionally, all mailbox providers have some verbiage in the terms of service and acceptable use policy that centers around customer data use, especially regarding feedback received and its use in filtering decisions. While making these decisions, mailbox providers can look at other signals like external blocklists, volume signals, etc., but TIS and TINS are direct reports from users and carry the weight of gold. In other words, all other factors in reputation calculation center around these metrics.

3. The common threshold discussed with clients for spam complaint percentage is .08%, yet we’ve heard that can vary by ISP. Is this true?

The first thing we need to realize is that ISPs calculate the spam complaint percentage differently from how email service providers (ESPs) would. This is due to the fact that ISPs have more data available than an ESP. 

Another crucial difference is that an ESP would rely on delivery rates for its spam calculation, while an ISP calculates the spam complaint ratio based on the volume of emails that reach the inbox vs. the complaint volume. 

Apart from being blind to inboxing rates, we don’t get TIS (feedback loop) reports from all providers, and not all providers share 100% of the TIS reports back to ESPs. So in effect, we cannot effectively calculate the spam complaint percentage. Additionally, ISPs don’t have a static threshold for the spam complaint percentage to determine reputation. For example, a transactional sender usually has lower complaints than a bulk sender, so utilizing a static value wouldn’t make much sense. 

The best way to monitor spam complaint thresholds is to benchmark the percentage with your historical volume, reputation signals, and engagement data and create thresholds. As an ESP, we could take a holistic look at similar data, but those would just be guidelines, and it won’t trump your historical data.

4. In your experience, how much does content (email body, subject line, URLs) actually matter from a filtering perspective? 

Content plays a significant role in filtering, especially URLs and domains. And since spammers have moved to free email providers to send unsolicited mail, content reputation is necessary to combat unsolicited mail because IP/domain reputation by itself isn’t reliable. 

For example, if a URL/domain has enough complaints, there’s a good possibility the ISP will block it, or mail having this domain will go to the spam folder—although email signatures and email hashing have also long identified harmful content. 

Another favored technique by spammers is to break content filters using long-coded URLs/hexadecimal URLs and IPs with URLs. In other words, adding a text version to your content goes a long way in easing the filters from all that mangling and deciphering of poorly coded HTML.

5. A common saying about email deliverability is that it’s not a “set it and forget it” solution. Can you explain what that means and why it’s important for marketers to take that message to heart? 

Simply put, as ISP email filters evolve, so should your email program.

6. Does brand recognition play a role in email deliverability? 

Email branding plays a crucial role in last-mile email deliverability. That’s because filters like to tag/classify email appropriately, so having your brand aligned across the visible From address, return path, reverse DNS, and DKIM d=domain will help build a quicker reputation for your brand. 

Just remember that brand identification starts with clearly identifiable information, like the website and the Whois record of the domain/IP. To prevent those cousin domain attacks that have become quite common, ensuring you have the technical parts (authentication) set correctly helps reduce the damage to your brand.

7. What has been the biggest difference in your approach to email deliverability regarding switching from a postmaster role to a consultant? 

As a postmaster, the goal is to ensure legit emails get delivered to the inbox while, at the same time, ensuring your customers’ protection from malicious emails. 

But as a receiver, you see email from on-prem complicated systems to large ESPs, so you deal with everything from poorly coded software to zombie networks. Additionally, at an ESP, we know the technical bits are taken care of and can concentrate on the finer details of email marketing.

That said, there’s always a fight between spammers and marketers to get to that top shelf, and our job, as deliverability consultants, is to educate marketers to not look like spammers. So in that sense, not much has changed, as I still look at deliverability from a receivers’ perspective.

Thanks to Sridhar! And be sure to stay tuned each month, as we’ll chat with another expert in the world of email marketing to provide you with further insight into the ins and outs of email deliverability. 

Until next time, check out Twilio SendGrid’s Email Deliverability Services packages to get started, or contact our Sales team to learn more about improving your email deliverability.

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