Wednesday, 6 November 2019

EMAIL DELIVERY GUIDE: Tactics Every Marketer...


Email is one of the most essential tools used for communication, may it be transactional email or marketing email. It does not matter what other communication media one is using, email is used for sure with no second thoughts.

Email sending channel is most appropriate and trusted channel by almost every enterprise (essential or non-essential).

Major communication mails include;
  • Regular or new invoices
  • Registration/Order Notifications
  • Sales and Discount Offers
  • Marketing Mails
  • Updates
  • Newsletters
& Many more…..

So, we know that email service is deeply integrated with all small, medium and big enterprises for many scheduled tasks every day; but is it a successful channel? Are all mails delivering to inbox?

This is our main concern and through this guide, we will talk about what are the do’s and don’ts in email communication which somehow will help assuring inbox delivery instead of junk or spam folder.


Simply speaking, email delivery refers to reception of incoming email in the primary inbox. Nature of email can be anything; marketing or transactional. This is also known as "successful email delivery".

If the mail is delivering in junk/spam folder of receiver or is entirely blocked by the internet service providers (ISPs), then we call this a "failed email delivery".

Most of businesses who rely on email communication as major communication media are suffering from failed email delivery as they are either not properly educated or are not following the terms and conditions as framed by the ISPs.

Once majority of mails fail to arrive, being either blocked or spammed, then people awake to find the cure. There are many false assumptions made related to email delivery- one of which is "Low Bounce, High Inbox Reach".

Now, bounce percentage defines the quality of data and subscription validity. So, it is important but not the only factor for failed email delivery. There are many hidden technical facts which cannot be understood by every person but every business needs a dedicated team to understand these facts and implement in the emailing process for improvements.

The failed email delivery may prove fatal as these are not simply promotional mails, which if not delivered will not bother your revenue.

We are here discussing the "ONE to ONE" emails which include: order notifications, invoices, password reset, verification mails, regular and critical updates, registration confirmation mails, important marketing mails.

If such mails are delayed or went to spam or are missing altogether then it will hamper your business graph upside down. You can calculate the revenue loss by simply calculating that how many mails you sent and out of whole lot how many were actually delivered. This will help one to calculate loss on every single email left undelivered.

Delivering mails directly to receiver’s inbox ask a lot of homework to be done by the sender solely. A complete practical study of all factors is required which keeps on changing from time to time based on behavior of both sender and receiver.

Recommended: 101 Actionable Email Marketing Tips (That You Can Implement)

ISPs & ESPs (Basic Difference)

Internet service providers commonly and logically refer to those companies who are main source of the internet like Comcast, Verizon, CenturyLink, Time Warner etc.

But in email industry, the reference is made to inbox/email service provider which instead of abbreviating to ESP is wrongly abbreviated to ISP, but also correctly read as inbox service providers.

Gmail, Yahoo, Live, Outlook all have their individual setups and T&Cs. If these terms are not followed by the senders then email may end up landing in spam or will be blocked altogether. Delivery terms, active filters, authentication and behavior of recipients will analyze the status of every mail before landing into primary inbox.

We have discussed more on this topic separately and in full detail in another guide. Make sure you do not lose your sender's reputation for regular email delivery. 


Reputation doesn't build in a day and so is the case with email sender reputation. This is a hefty work which needs time, hard work & focus. Now, a sender should know that T&Cs are not common for all the ISPs as each has their own algorithm for authentic email delivery.

Top of it, these terms keeps changing so if you email id delivering today, there is the probability of spam delivery on secondary inbox delivery of the same email. Delivery success also depends on Sender Reputation. So, keep your ingredients ready for successful email delivery. 

The big question is, how to deliver your mail to the inbox of a receiver?

Simple answer by ISPs is that you maintain your reputation and we will deliver your mail to an inbox. Another question is how to define sender reputation, the answer to which will be covered in coming sub-topics.

Interaction/Engagement Ratio + Domain & IP Reputation + Email Content + Spam Complaints + Spam Traps + Invalid Email Database + Blacklists + Third Party Links Insertion

#1. Interaction/Engagement Ratio

Whenever email is received, action happens on it by the receiver. This action is open, click, unsubscribe, forward to friend, reports spam etc. which we may check easily in our email platform statistics area.

There are some other factors or actions as well which helps ISPs decide the reputation. You may not see these in your statistics area but they hold equal importance.
  • How many times receiver opened the email
  • How many times mail message is forwarded
  • Is it deleted without reading or after reading
  • How many links were clicked
  • Movement of mail message from one folder to another
  • Any extra tag added to mail or not
  • How often is it added to contact list
These responses and behaviors are noted by the ISPs and have some weightage in overall reputation. These hidden statistics will also add points to overall reputation.

So, if you have not revised your definition of reputation then you are lagging behind in the competition. 

#2. Domain & IP Reputation

Domain and IP are required to initiate the email sending process and good delivery will depend on how much reputation did the domain and IP have scored.

Domain: If you are using domain to link with your subscribers for transactional or marketing nature of mails, it must be your active domain with running/live website. Sometimes vendors keep the provision of domains with a good reputation but it is ok for marketing type of mails.

In the case of transactional mails, one should use own business domain to gather the highest interaction. This is because people subscribed to your brand name which they will recognize through sending domain. Using random domain will not work as it develops distrust among subscribers. 

IP: Vendors make sure to serve an already warm up IP to their customer which can be used to get success delivery in inbox. IPs with zero or negative reputation results in low interaction or even failed delivery. So, best is to hold your mailing and warm up your IP for best results.

Domain and IP are two different entities. If the reputation of your domain is good, doesn't mean you can use fresh IP for good delivery and vice versa. Thus, reputation of both entities holds equal importance. Prior to sending your emails, make sure to check the warm up status of IPs and reputation points of domains involved.

#3. Email Content

An email campaign comprises of text content, images, links, source code, design & texture. So, consider the following important things before your team start starts creating email campaign design.

Use Original Content: This is also a part of content marketing, so it is important to use original words and sound fresh. Copying the content from somwhere on internet and using it may prove degrading leading to less interaction.

This is because you are not aware who else have used that same content and ended up spamming. Better is to not take risks as it will consume much of your time to generate new text.

Apart from this using one campaign multiple times for same or different purpose can be lethal too for sender reputation. It is easy to copy the content or the whole design from internet, make some minor changes and use it. But you cannot identify the spam keywords, spam links, or spam tags which ISPs do notice.

Once noticed your mail will be spam too leading to blacklisting of your domain and IPs. 

Source Code: Most of the senders do not bother incorporating any kind of changes in HTML coding. Using CSS, JavaScript in a mailer, table designs may lead to a less responsive mailer ultimately resulting in distortion when opened in different inboxes. Sometimes we copy paste the source code and make the changes only in text and image part.

But ISPs are quite smart as they check each and every part including the tags and tables etc. So, if you are using a blacklisted design's source code then your new mailer might get blacklisted too by ISPs.

Keep the size of mailer within 600px dimensions and make sure the unsubscribe link is mentioned in it. It asks for extra time to design a campaign from scratch but its worth to increase the revenue. 

Link Shorteners & Image Hosting: Use of link shorteners (which are mostly used by spammers to hide where they are redirecting receivers), free image hosting service is a native style of spammers as they have to hide their origin and ultimate landing page.

Also, these links and images might be already blacklisted and used which will make your campaign appear doubtful by ISPs. Sender reputation will be affected which will lower your interaction rate and worst is your primary business domain gets affected. 

Avoid Repetition: Say, you have designed one campaign and using it for transaction/marketing mailing purpose to send to your subscribers. Now, what when the same design is used for affiliate mailing too. The reputation and engagement of tranasactional mails are high and when the same is used for affiliate mailing, it may help.

But the reverse may not help as bad reputation of affiliate mailing may degrade the transactional email delivery. This won’t take much time to generate two separate mailers for a separate type of mailing. Keep subscriber mailing completely separate form affiliate mailing.

Engaging Content: Try to be creative when it comes to your email campaign design as your subscribers will engage only to creative content and engagement is very important for revenue. Make your receivers compelled to open your mailer becuase if email remains unread your subscribers will not receive latest updated and you will lack the responses.

Get some more insight on engaging email content by reading this post.

#4. Spam Complaints

Sender reputation may not get much affected by spam complaints but whenever a receiver marks your mail as spam (Report Spam), ISPs do note it and mark your content as blacklisted.

So, this poses a negative effect. Spam complaints is acceptable when ratio is 1 on 100. People look for Report Spam mostly when they fail to find out easy unsubscription option.

So, it’s good to show "Unsubscribe Me" in big and bold. Also, make sure your subscribers identify you. If identity is hidden, person may either ignore, delete or report spam. 

#5. Spam Traps

There are some email addresses which are not supposed to receive any mails, these are defined as Spam Traps. Those category of email addresses which are either very old or not used for a long time comes in the category of Recycled Spam Traps.

Some email addresses which exist but have not signed up for any service (created to identify spammers), are called Pristine Spam Traps.


Cleaning data by filtering old email addresses from database will rescue from recycled spam traps and pristine spam traps. Further, these traps can be rescued by avoiding usage of purchased database, or randomly collected database.

Pristine spam traps are true trap to find out those who do not follow authentic email methods and this category of traps are created by ISPs or blacklists for a regular check.

#6. Invalid Email Database

Avoid using the database which is older than 6 months. Before sending mails to your subscribers, this is necessary to find our total invalid, inactive email address. High bounce does affect the sender reputation and bounce number is high when data is not valid.

A welcome mail soon after registration helps filtering invalid email address. Sending regular newsletters or mails to subscribers too helps to generate an engaging and non-engaging contact list.

Before sending any email campaign to your subscribers, make sure the list is fully active because even if 5% data is dead then ISPs consider it bad for sender reputation. 

#7. Blacklists

Blacklists are monitored by the ISPs to find out the nature of sender. If high number of spam traps are found the IP, links, domain and the content will be blacklisted which thus blocks the mail reception from the same sender again from same IP and domain.

IP whitelisting is a gradual and slow process, so it’s better to practice genuine mailing. Sending relevant content after seeking permission helps avoiding blacklists.

#8. Third Party Link Insertion is one company whose mailer is sent but if in the mailer the links used are associated with then this is a problem. Links inserted in mailer must be legitimate and associated with the company whose mailer is sent. Also, third party links carry the risk of blacklist. If you are a genuine sender, use authentic information. 


Front end is clearly visible & hence is simple to apply and understand and improvements can be applied whenever requried. But the back end requires skills to control as it is not a part clearly visible. A perfect knowlege and technical skills are also required by the team to handle and maintain. 

Framework (IP Address, Servers) + Authentication (SPF, DKIM, DMARC, MX, PTR)

Framework is made up of servers and IPs which are used to send the mails. Authentication is validation technique to confirm that mail received from you exactly belongs to you and came from your system.

There are more than one responsible factors for a mail to land in inbox including the framework and authentication.

#1. IP Address

What is your mailing structure: shared or dedicated? Whatever structure one follow, it makes a full report of how you practice email marketing. This is hence responsible for building your reputation as a sender.

#2. Servers

Servers can be located either in your locality or in foreign places. The location matters and hence the email deliverability.


ISPs consider authentication critical for better email delivery. Each and every authentication separately plays its role individually.

########a.  What is SPF?

Sender Policy Framework: SPF is a DNS record which when created in a domain helps tracking which IP is used to send mails using your domain. Make sure to create the SPF records for all IPs used to send mails. If there is any IP sending mails using your domain with no SPF records, then mails may land in junk/spam folder or will be ultimately blocked by the ISPs.

########b.  What is DKIM?

Domain Keys Identified Mail: The message which you have send is similar to the received message or not, this is confirmed via DKIM records which are made in DNS records of the domain. This is necessary to bypass certain malicious intermediate activities and to ensure correct delivery. DKIM failure is considered negative by ISPs, thus landing mails either in junk folder or are blocked altogether.

########c.  What is DMARC?

Domain-based Message Authentication, Reporting & Conformance: If a domain is not signed with DKIM & SPF then DMARC is authorized to decide to receive mail, reject mail or filter mail. This is another factor which will decide the sender reputation by deciding the domain reputation. For implementing DMARC one needs to check all the IPs which are sending mails and whether these IPs are listed in SPF or not. If not then DMARC will take next decision.

########d.  What is Dedicated IP structure?

One IP, when assigned for one type of site or mailing, is called dedicated. Sending mails using 1 single IP is called dedicated IP structure. Mails, when sent to your subscribers, are practiced to be sent using dedicated IP structure. This is beneficial as there will be no impact of one another on different types of mailing.

For example if we use 1 IP for marketing mails and another for transactional mails, thier reputation effects will be independent of one another. If your usage is above 50000 mails/month go ahead and use dedicated path which is considered responsive for consistent and high volume senders.

########e.  What is Shared IP structure?

One IP associated with multiple sites or domains to send a variety of mails is called shared IP structure or route. So, basically mailing of and are done form a single route and if say, indulge in illegitimate mailing or develops negative reputation then will also suffer.

If your monthly traffic is below 50000 mails, then no need to think much and use shared path becuase a low number of mails are sent every hour and thus reputation will be least affected. Also, sometimes one may get the benefit of the good reputation of another. So, a win-win situation.

########f.  What is A records & PTR records?

Pointing domain to an IP makes A records and linking an IP with domain generates PTR or pointer records. These records helps making white-labelled structure and holds a good impression over ISPs.

########g.  Sending domain with MX records?

The domain which is used to send the mails must be an active domain which we can define as a domain which is active on mailbox. This domain should receive mails and send mails. Also, MX (mail exchanger) records are necessary to helps ISPs find out status of your sending email id and make it white-labelled.  

########h.  FBLs (Spam feedback loops)?

All mailbox providers have their own configured spam feedback loops to gather the complaints from end users. This report is then shared with the ESPs to remove the email id and not to share any kind of email with the person who complained.

good email service provider is expected to be registered with all major FBLs to avoid consequences from ISPs and maintain a good reputation. Every ISP have their own unique way of providing the option to mark the complaint.

########i.  Postmaster & abuse mailbox?

Most of MPs or ISPs demand postmaster and abuse email ids by all ESPs for registration on FBLs. These MPs share the complaints on these email ids so it is also necessary to open them from time to time to be updated of any new complaints and remove them from database.

If in case ESP is not registered on FBLs, then complaints are also sent on postmaster ad abuse email ids. So, either you are registered for FBL or not you should have postmaster and abuse email ids with regular monitoring.

########j.  Segmentation of variety of mails?

This is useful for the high-volume senders who are sending a large number of mails of different categories and also are using dedicated IP. Using dedicated IP is recommended for sending large bulk but One Mail One IP option is far better than All Mail 1 IP.

The difference is as discussed

Say you are sending transactional mails (passwords, receipts, invoices, verification mail, registration mail etc.) form 1 IP and using the same IP to send your marketing mails which is not a good practice. Marketing mails often may fall in promotion tab instead of primary inbox but transactional mails are to be delivered in primary inbox only.

But if single IP is used the impact of marketing mails will fall on transactional mails too.

So, the best practice is to use separate IPs for separate streams of mails. Your ISPs will be happy too and this will helps gain positive ranks in terms of sender reputation.


The message which you are sending, will ultimately decide the fate of your email landing either in inbox or spam. It is very necessary to match the content of a mail with the stream/category of mail, for example, if you are sending a transactional category mail and your content mention some promotional lines or format then delivery will be affected.

Also, who is your email receiver also matters? Sending mails to people who never subscribed to your service is spam.
  1. Take permission from people and do not barge in without subscription confirmation. A proper registration and verification will complete this process.
  2. Send what your subscribers permitted for. While subscription makes sure to mention all options open for subscriber to choose from and send the mails of only those categories. Do not just fill in the receiver’s inbox with all your mail when he asked for only selected ones.
  3. Provide option to choose. Let the subscriber choose the category he/she is interested in. Send only those mails which subscriber asked for. Keep your subscriber happy.
  4. The welcome message is very necessary for subscription confirmation. This mails should be sent soon after registration is complete. This will show your quick action and professionalism towards every new subscription. Along with this, these mails help filtering inactive email ids too, thus, reducing bounce ratio.
  5. Interaction ratio. After sending mails response of your subscribers is very important. Opens, clicks, forward to a friend, unsubscribe, open and delete, direct delete; these are some interaction behaviors by the receivers.

    Based on these statistics, one can decide that which type of mails people like to receive and which not. Those subscriptions who are not responding, it's clever to remove them from the contact list. Focus on only those who are your regular readers.
  6. Easy un-subscription: Let your subscribers leave you whenever they want. If we do not provide a direct option, we are forcing them to click on Report Spam button which thus will deteriorate your ISP reputation. Make unsubscribe option one step and easily visible in the mailer; at the top and at the button, bold and clear.
  7. Sending frequency. Follow the practice of sending mails to your susbcribers based on the subscription they chose. This can be weekly or monthly or daily. It's chaos for users to receive mails weekly when they asked for monthly. 


THANK YOU for reading!

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