Getting Started  with Email Deliverability

Before sending your carefully-crafted email campaigns, it's important to first understand a few basic ideas and rules of email marketing to ensure your campaigns are successful. In order to achieve good open-rates and click-rates, and to keep your emails from landing in the spam folder, you must first earn your subscribers' trust. The factors that play an important role in improving your email deliverability, while also gaining the trust of subscribers are:

Email Authentication

Before an email gets delivered, it is first validated to ensure  it's  coming from a safe origin. With  phishing attacks happening every day all over internet, it's  important to prove how safe and secure you are.  That leads us to an important question. How can you prove your emails are from a safe origin?

Any email  you send has to first be authenticated. Based on the status of authentication, emails get classified and then delivered to the inbox (if authenticated properly), quarantined, or  sent to the spam folder. Email authentication includes validation techniques such as:

  • SPF (Sender Policy Framework) - to authorize sending sources.
  • DKIM (DomainKeys Identified Mail) - attaches Domain Key to encrypt the message and is inclusive of SPF.
  • DMARC(Domain- based Message Authentication, Reporting and Conforming) - prevents illegitimate usage of domain name in sender address.

By default, Zoho Campaigns performs authentication for all email sending domains. We  highly recommend you to authenticate your domain to avoid phishing attacks.


"The Sender Policy Framework (SPF) is an open standard specifying a technical method to prevent sender address forgery. "  Source: SPF

An SPF is a record that manages IP addresses which can send emails from your domain. It is the authentication of the sending source.  If an email is sent from an IP address that is not on your list,  it'll be treated as if it's from an untrusted network. This is a common reason many emails land in the spam folder. 

If you are sending emails through Zoho Campaigns, then you have to authorize Zoho Campaigns to send emails on your behalf. Learn more.


"DomainKeys Identified Mail (DKIM) lets an organization take responsibility for a message that is in transit. The organization is a handler of the message, either as its originator or as an intermediary. Their reputation is the basis for evaluating whether to trust the message for further handling, such as delivery." Source: DKIM

In ancient days, when a letter was sent from a high-ranking official or emperor, it would have been sealed. If the seal was unbroken, the recipient had full confidence that the message had not been altered in any way. Similarly, when emails are sent across the internet we must make sure that the email is not intercepted or altered before it is received. DKIM encryptions confirm that a message sent from the sender is not affected and is identical to the original message. Learn more.


 "DMARC, which stands for “Domain-based Message Authentication, Reporting & Conformance”, is an email authentication, policy, and reporting protocol. It builds on the widely deployed SPF and DKIM protocols to improve and monitor protection of the domain from fraudulent email." Source: DMARC

DMARC makes  it  impossible for a user to see a fake/fraudulent email from a brand’s domain name. In short, it helps conserve a domain's reputation. This is the latest protocol that was recently formulated to ensure good deliverability to reputable inbox providers. Complying to DMARC policy is an added advantage. DMARC tells ISPs and ESPs what actions emails can take without passing SPF and DKIM.  Learn more.

Emails sent from authenticated sender domains will build good reputation with email filters. Thus, you can reduce the probability of your emails ending up in the spam folder.


Sender Domain

We recommend you use an email address with either your organization's domain or sub-domain. Eg: or

The domain from your official website and the domain you use for sending campaigns must be related. For example, if your website is then your email address should be something like or However, if you use something like, then there's a higher chance  for the subscriber not to recognize you. The user should be able to easily recognize  the email address and the company attached to it. 

Domain Blacklist check-up

Before sending an email, make sure your  domain isn't blacklisted. Blacklisting depends on the sender's reputation. You can check the reputation of your domain at Sender Score, SenderBase, or other services.

Check your domain reputation with leading Anti-spam or Blacklist service providers  Spamhaus, Sorbs,  Spamcop and others.

If your domain is blacklisted, try  and reach out to  the concerned anti-spam service provider and ask to De-list it, or if possible, try to white-list it.


Subscriber management is one of the most important factors for a succesful  campaign. Having more subscribers is not necessarily the goal, but managing them properly and efficiently in order to reach the right audience. 

Contact segmentation

Contact segmentation is the process of categorizing your subscribers based on the people you specifically want to  target for a specific campaign. Let us imagine that you want to invite your subscribers to a webinar on pencil making. Your contact list may have pencil makers as well as box makers, laptop makers and pen makers. Your email would be useful to pencil makers but the others would ignore it or  even mark it as spam. Such scenarios happen often in email marketing so it's really important  to segment your subscribers.

Contact segmentation is based on target marketing. A target market is a group of people considered likely to buy a product or service. A target market consists of customers who share similar characteristics like age, location, income, and lifestyle, to which a business directs its marketing efforts and sells its products.

Your opt-in list may contain contacts with which there might not be communication in a significant duration (6 months). When you send an email now they might not recognize you and hence may mark you as spam. Convert them into opt-in contacts by sending re-engagement emails and while doing so, introduce yourselves. If they are still not responding you may eliminate them from your list. Learn More

Email campaign frequency

Sending emails regularly is great, but if you send them on a too frequent basis, like once a day, your recipients  may become annoyed and lose interest in your brand.  If your emails begin flooding your recipients' inboxes, they might mark it as spam or unsubscribe. If your email count is high  the proportionate spam complaint will also be high, thereby damaging the aggregate results. This act of sending too many emails in a short duration is called campaign burst. To avoid this you can choose a pattern in your settings (if you are an admin). 

  • Per day not more than one email can be sent.
  • Per week 2- 3 emails can be sent
  • Per month maximum of 8 emails can be sent.

The frequency interval between two campaigns should be at least one day. If you want to send a campaign, but  your campaign limit has exceeded, then the admin from your organization will have to make changes to the settings. Additionally, it is advisable to segment your subscribers and send emails to a specific crowd  you want to reach. 


Bounces occur when sent emails cannot be delivered. Typically, the email server will send you an error message detailing the reason for the bounce. To learn more about this mechanism, read here.

Email throttling

If you are sending emails to a large number of customers in the first attempt  then  suspicion will arise among an email recipient system. Let's say you have a million subscribers. Suppose many of your subscribers belong to one or few recipient systems (for example,  600,000 of your million subscribers are Gmail users and 200,000 subscribers are Yahoo! users), then the following scenario will occur. If you are new to that recipient system, say, Gmail or Yahoo!, and  you are sending large number of emails in the  first attempt,  the recipient system may view that as suspicious, usually because you don't have any footprints with the recipient system. Until you build good reputation with the recipient system, it may defer your emails.   The best solution to  this is to segment the contact list and to gradually increase the number of email recipients. For further details on email throttling, learn more.


The content of the email includes the following:

  • Subject
  • Message to be conveyed to subscriber
  • Sender logo
  • Images 
  • Footer


The subject of an email is like the head of a body. It's one of the first things a receiver observes when he or she receives an email. Open rates of your email campaigns depend greatly on  your subject line. That's why it's crucial to spend a lot of time crafting this part of your email.  In general, the subject needs to be:

  • Short and crisp 
  • Free of spelling or grammar errors
  • Avoids false promises

Sender Logo

When you are sending emails to your subscribers it is important that they  recognize you easily. Including your logo in your email content gives more trust to the subscribers. Your organization more than likely has a standard format/layout when positioning your logo so make sure to follow that position and format it in all your emails. 

Email Message

The purpose of sending emails  is to convey the message you want to deliver to your subscribers. It's important to position your content  in such a way that  doesn't create suspicion among spam filters and recipients. That's why  Zoho Campaigns reviews your content before  sending it to recipients. 


Image-text ratio should be maintained(40:60) and image dimensions need to be accurate and standardized. 

Make sure images have good resolution and  are easily loadable for your subscribers.


Each business related communication must contain a legal notice. This information may be included in the email as a whole (this method is preferred) or by adding a URL.

  • Name of the sender or company name 
  • Authorized representatives
  • Postal address of the sender
  • Telephone number, fax number or electronic contact form 
  • The sender's email address  
  • Commercial, cooperative, association or partnership register number 
  • Naming of the publisher or person responsible for the content of the email 
  • If available: Tax Identification Number or business identification number 

This information must be: 

  • Easily perceptible
  • Directly accessible 
  • Permanently available

If you have a disclaimer make sure to include it at a specific location that is constant across all emails.
           Include "Unsubscribe" option in all your campaigns.
           Keep footer in resemblance with the footer in your official website.

Using URLs

  • If your content contains any URLs,  make sure that they are from domains that are easily recognizable to your subscribers. Using  non-business domains leads to suspicion among spam filters and subscribers and may result in emails getting marked as spam.
    Example: If your sender address is, then the URLs you use can be from domains such as,,,, etc, but not from non-business domains such as,, etc. 
    So, before sending emails check whether your URLs are from business domains.
  • The URLs you use in your content should not  have multiple redirections. One or two redirections are acceptable but not any more than that.
  • Shortening URLs from public services is not advisable since it may have multiple redirections or may get blacklisted easily since it is vulnerable to many attacks.
  • URL Blacklist Checkup

    Verify whether your URLs are being blacklisted before sending emails. If they are blacklisted then you have to "de-list" them. Check reputation of URLs to be used with leading Anti-spam or Blacklist service providers Spamhaus, Sorbs, Spamcop and others.

Sending practices

Email recipients may have their email addresses in various inbox providers like Gmail, Yahoo!, Outlook, etc. In order to  improve your deliverability you should familiarize yourself with a  few rules on sending emails to various domains. 

Inbox providers analyze the spam markings in  emails  before they get delivered. Depending on the content, emails are filtered by spam filters in system level (by ESPs and ISPs). Users can also mark emails as spam at subscriber level. Based on the responses of your email recipients, they maintain a reputation for sender email address and domain. If you have a good reputation, you'll also have a high deliverability rate and favorable reputation. In order to keep your reputation high with these inbox providers, it is essential to have good rapport with your subscribers. Remember, every single spam marking by your subscribers gradually reduces your reputation. 

  • Zoho Campaigns strongly recommends you  follow permission-based email marketing. Ensure that all of your contacts are opt-in.
  • In content and subject, avoid words such as buy, order, discount, clearance, dear friend, as seen on, please help, free, offer, desperate, additional income, etc.
  • Email subject may not convey the message you actually intended for your subscribers. Due to this your subscribers may get mislead and mark you as spam. Ensure that your subject and content are relevant to each other.
    If your subscribers are Gmail users, look through these pages to learn more on how Gmail marks an email spam and how to improve the sender reputation with Gmail with respect to:

Getting your emails delivered in Gmail not only means getting them  through spam filters but also getting into the Primary tab. Emails in Primary tab get more attention. If your emails end up in Promotions Tab then the open rates and click rates will be significantly less. Promotions tab is where many marketing emails land. Because of this, lots of marketers get a  reduction in deliverability. Read more for information on Gmail tabs.  


          Succesful email marketing campaigns begin and end with preparation. Not only do you need an organized subscriber list along with creative and valuable content, but you also have to make sure every campaign satisfies a number of conditions before you click 'send'. At Zoho Campaigns, we hope all of the elements we discussed here will give you an enlightened perspective to improve your email deliverability while decreasing bounces, unsubscribes, and spam markings to improve your email deliverability in the future.