Start your free trial with WA EasySendy today!

Start your free trial with WA EasySendy today!    Register Here

The Concept of Micro-Deliverability in Email Marketing

by | Mar 9, 2023 | Blog, Email List Management, Email Marketing, Micro-Deliverability | 30 comments

Micro-Deliverability is a relatively new concept in the email marketing domain. It involves drilling down into deliverability by domains, or ISPs or SMTP Relay servers and then segmenting the email list or campaigns based on the results to get best deliverability and performance for the marketing campaigns.

The best SMTP relay service providers have the overall deliverability rates of above 96%, but these deliverability rates keep on fluctuating based on ISPs as well as time.

By carefully tracking these fluctuations of deliverability trends based on ISPs and time, one can route their emails for different segments using SMTP delivery servers that deliver the best performance for that particular segment.

Thus, using more than one email delivery system (Hybrid System) can significantly enhance your email marketing performance.

The concept of Micro-Deliverability in Email Marketing


By redundancy, we mean, having more SMTP relay servers ready for use than you actually use. This redundancy can be a great asset to have at the worst of times.

When there is a temporary outage or significant drop in deliverability for a specific SMTP relay server (for a particular segment), redundancy gives you the flexibility to immediately switch the relay server for that segment without impacting performance and deliverability.

Email Filtering by ISPs and Deliverability Issues

Email filters are a fact of life, especially for an email marketer. They are a necessary evil to filter out spam. But sometimes, legitimate email messages are mistakenly filtered as spam or sent into junk box.

This is the collateral damage of email filters. The sender’s reputation causes many deliverability issues, but some issues are related to the SMTP relay service providers too.

Why Email Filters are required in the First Place?

According to Symantec, nearly 70% of all email sent is spam.

These include phishing messages, malware, emails coming from spammers who leverage this channel for nefarious purposes. If no filter existed, inbox delivery will increase. For every useful email, there will be two spam emails.

This would make the whole email channel useless. Email spams are the reason the ISPs filter emails.

Causes of Email Deliverability Issues

There are multiple reasons why a legitimate email ends up in a spam folder rather than the inbox. Some of these are related to the sender’s reputation while others are related to the email service provider the sender is using.

[bctt tweet=”Authentication, Bounce & Complaint Management, IP Reputation are the major cause of Email Deliverability Issues.” username=”easysendy”]

Sender Issues

Sender’s reputation is considered in deciding whether an email will reach an inbox or the spam folder. Multiple factors determine the sender’s reputation. These factors are as mentioned below:


ISPs rely heavily on authentication to make sure that the stated sender is the actual sender of the email. ISPs use three different authentication methods to do the authentication:

  • Sender Policy Framework (SPF)
  • Sender ID
  • Domain Keys Identified Mail (DKIM)
  • Domain Message Authentication Reporting & Conformance (DMARC)

These authentication methods allow the ISPs to compare email information with the DNS records about the email sender.

If the email information does not match the DNS information, there are more chances of the email landing in the recipient’s spam box rather than the inbox. If the sender’s authentication is not in place, the sender’s reputation will deteriorate.

2. Spam Complaints

If the recipients are reporting sender’s emails as spam, the sender’s reputation will deteriorate.

Spam complaints should be less than 0.1% of the total sent volume for every email. Sender’s reputation deteriorate in case of 0.1% on consistent basis.

3. Bounce Management

Sender’s reputation reduces with repeatedly emails bounces. It shows the ISPs that the sender’s email list is not clean.

The industry standard is to remove hard bounces after one occurrence and soft bounces after three consecutive sends.

4. Recipient Engagement

A sender’s reputation gets damaged when the recipients to whom the sender is sending emails aren’t opening those emails.

In other words, the clicking/ opening rates are low. This detail shows that the recipients to whom the sender is sending emails are not interested enough in those emails.

SMTP Relay Issues

SMTP relay issues hamper email deliverability. The most common problem is related to shared IP addresses. Although the ISPs are moving towards domain-specific filtering, most ISPs still filter at an IP address level.

This means that if an IP address is sending emails which are perceived to be spam, all emails from that IP address will be blocked regardless of the domain it is sent from. Even from a dedicated IP address, which is used by a single entity, one can experience SMTP relay side deliverability issues.

Hindrances to achieve Optimized Micro-Deliverability

1. Scarcity of Micro-Deliverability Data

SMTP relays publish their overall deliverability rates on a monthly or a quarterly basis. They do not have resources to post them more frequently.

Even in these publications, the deliverability rates are overall rates, not by Domains/ISPs. These overall rates cannot be used for Micro-Deliverability optimization purposes.

2. Lack of Time

Even if the data would have been available for Micro-Deliverability Optimization purposes, the time taken to arrange that data and then use it for email segmentation purpose is unfeasible for the email marketers to carry them practically out.

3. Single ESP or SMTP Model

Most organizations tend to have a single ESP or SMTP model. This is because learning and using multiple ESP or SMTP relay interfaces, sending emails from multiple SMTP interfaces and aggregating the performance data from each one of them is time-consuming and unfeasible, to say the least.

About EasySendy PRO

EasySendy Pro is an email marketing platform for the digital marketing team. It integrates with multiple SMTP relay service providers and enables delivery of email campaigns to a list of opt-in emails.

You can split test email deliveries across the relay servers and check reports, track email clicks, opens of each email campaign. It also has smart autoresponder and email list segmentation.

To support Micro-Deliverability in Emails; currently, EasySendy Pro allows integration with SMTP relay gateways like Amazon SES, Mandrill, SendGrid, Sparkpost, Leadersend, Dyn, Elasticemail, MailGun, SendinBlue, MailJet, TipiMail, and MailerQ. If you are sending an email to a list of above 25,000 email subscribers, then, Micro-deliverability of the email through multiple SMTP gateways provide better email open rate.


  1. jai

    Hi Ankit,

    In case I use easy sendy pro, is you or your team can help me integrating AWS to it. For AWS what ever it takes, I will get that done with your team’s help.

    Will easy sendy pro gives me email templates samples, click and drop editing of emails, automation sales emailers, trigger based emails, etc.?

  2. Paul

    so if I have a list of 20,000 gmail addresses (not mixed, just gmail), is 1 smtp enough?

    • Ankit Prakash

      Hey Paul, if this is the case then you should build good email sending reputation through 1 SMTP relay server. Do the proper technology setup like, SPF, DKIM, DMARC and other setup and follow healthy email marketing practices.

  3. Charles

    I agree ! Switching to the best SMTP relay servers can actually increase your deliverability rates. Not only deliverability but also there are various aspects on which this statement proved to be true such as productivity.

  4. Richa Gangwani

    Good one! This seems to be interesting.
    Check out a platform where founders/Innovators can submit their startup, for getting feedbacks, beta subscription, early adopters, traffic and users.

  5. Aby Carrier

    Is your solution a hosted version of Sendy ?

    • Ankit Prakash


  6. Imogen

    Well, you must have heard about micro-deliverability in e-mail marketing. But somehow there is no such effective writing as this one on this subject. This blog has dealt with the concept in an absolutely different way for the people to read and understand it. Every point has been discussed clearly. Better read it for a proper understanding. Easysendy pro is an effective platform for micro-deliverability in e-mail marketing.

    • Chandana

      Thank you ! Yes, Micro-deliverability is relatively a new concept and that’s why our content team decided to chalk up some content on it! Glad you liked it!

  7. James Robinson

    Whilst this is a noble thing to claim – years of working with Ongage and other systems using multiple SMTP relays actually contradict this. Sending via multiple providers triggers Spamhaus’s legendary ‘snowshow’ blocks and alerts, often resulting in account termination with the SMTP relay provider effected.

    A better selling point for this would be that *if* you get dumped by a SMTP provider, you can quickly switch to another.

  8. Kristian Watters

    All excitement of marketers centers around deliverability. Some thing that promises a good 96% has all chances to become a marketer’s best friend. Micro-Deliverability sounds like a great tool. How much time does it take to execute Micro-Deliverability?

  9. Timothy Smith

    The existence of the Micro deliverable emails is new, now the deliverability rate of the emails has been ensured. It’s a path breaking innovation in the email marketing segment. Surely it can bring a change in the current standard mailing system.

  10. Mark Carter

    One thing I liked about this article is that every point is descriptive. Although, I didn’t understand the concept of bounce so can you please brief me about it? Otherwise a good read!

  11. Beverly Hill

    This is a great post, so clear and easy to follow. Micro deliverability involves drilling down into deliverability by domains, or ISPs or SMTP Relay servers and then segmenting the email list or campaigns based on the results to get best deliverability.

  12. Mildred Allen

    A very interesting post. Yes, Optimizing Micro deliverability can help us Email Marketers to increase the revenue by up to 33% according to a study. Since 25% of the emails sent by marketers are not delivered, it is a challenge to us email marketers to land emails into inbox.

  13. Donna Morris

    I absolutely loved this post, Ankit! Also by using more than one email delivery system (Hybrid System) one can notably improve their email marketing performance.

  14. Ronald Smith

    Micro-Deliverability involves drilling down into deliverability by domains, or ISPs or SMTP Relay servers and then segmenting the email list or campaigns based on the results to get best deliverability and performance for the marketing campaigns.

  15. Lori Butler

    Thanks for sharing this blog. I understood about the hybrid email architecture which can be setup to improve email open rate. I will soon implement this.

  16. Bradley Tate

    Hey, I have been searching on this topic. There really is very little content out there. Your article is quite detailed. Thanks for sharing

  17. Joyce Campbell

    Thanks a lot for the basic introduction of micro deliverability in email marketing.

  18. Ralph Diaz

    Hey Ankit! Thanks a lot for updating content about micro deliverability. If you want to increase the deliverability rates, you must switch to the best SMTP relay servers.

  19. Mary White

    Thanks a lot, Ankit, you have put great efforts in writing such a great article about the micro deliverability.

  20. Carolyn Ramirez

    Very well written! Thank you for sharing this concept of micro-deliverability in email marketing. I liked the way you have described all the details. Keep it up.

  21. Gregory Edwards

    Very well written! Thank you for sharing this concept of micro-deliverability in email marketing. I liked the way you have described all the details. Keep it up.

  22. Joseph James

    Great Article! Even with all of the new marketing technologies and tactics available to us, micro-deliverability is still the simplest that works best – email marketing!

  23. Alice

    Earlier, I was confused about micro-deliverability, but after reading this blog, I got a clearer picture. This article also covered the causes of email deliverability issues and a hindrance to achieving them.

  24. Ronald Stephanie

    Great article! I loved reading it and gained valuable insight into micro-deliverability. Yes, you are right that there are multiple reasons for email deliverability issues, and we need to overcome them to make our campaign successful.

  25. Jonathan Helen

    This article is easy to grasp about micro-deliverability and the reasons for email deliverability issues. Keep sharing such informative blog posts.

  26. Justin Pamela

    While scrolling down for micro deliverability articles…i found out your article which is quite interesting and i ‘ m impressed with the way to convey the meaning of micro deliverability. Now I have a clear vision about it because you used really simple terms that anyone can understand. Thankyou for sharing…


Submit a Comment

Your email address will not be published. Required fields are marked *