Getting started with email deliverability

Getting started with email deliverability

Identifying the needs and interests of contacts and conceptualizing email campaigns around those are part and parcel of a marketer's daily routine. Sometimes marketers may assume that crafting a compelling campaign alone will help them hit their conversion goals. This assumption is partially correct. However, marketers will have to do a lot more than just crafting a nice campaign—they will also have to work a lot to land it in the inbox. Once a campaign is successfully delivered, the campaign's content will take over and help you meet your conversion goals. So, achieving these is a two-step process where you first work to create a compelling campaign and work even harder to land it in your recipient's inbox.

The ability to land your campaigns in your contact's inbox is called email deliverability. This is a crucial factor that accounts for half of your campaign's success. To understand email deliverability, we're going to look at how Zoho Campaigns' email infrastructure works, how mailbox providers make inbox decisions, and the efforts taken by anti-spam services and mailbox providers to curtail spam.

Email infrastructure

At Zoho Campaigns, we've built a super-efficient email infrastructure that helps us offer seamless delivery of marketing emails. The core of our email infrastructure comprises the sender domain, IP address, and the anti-spam engine.

Sender domain

Your sender domain's reputation plays a major role in achieving inbox placement. When mailbox providers receive emails, they assess the sender domain's reputation to make inbox decisions. If the sender domain has a positive reputation, the chances of achieving inbox placement will be high. If the sender domain has a negative reputation, the emails may land in the spam folder.

At Zoho Campaigns, we urge our users to ensure that their sender domain always earns a positive reputation from mailbox providers and anti-spam services. The best way to start is by authenticating the sender domain.

Domain authentication

One of the major challenges that prevails in the email marketing industry is spam. To counter spam and safeguard their email, businesses adopt a lot of security mechanisms. One such technique is domain authentication. Domain authentication is the process of authenticating the sender domain by implementing a set of validation mechanisms. SPF, DKIM, and DMARC are the most commonly implemented validation mechanisms.

Spammers mostly purchase a sender domain and start performing email blasts without authenticating it. When you send emails without authenticating your sender domain, your emails may resemble spam in the eyes of mailbox providers. Hence, we urge our users to authenticate their sender domain before sending emails. Authenticating your sender domain ensures that the emails you send are not tampered with during transit. It also earns a positive reputation from mailbox providers and anti-spam services. This improves email deliverability and increases the chances of achieving inbox placement.

Click here to learn more about domain authentication.

Using a new sender domain

At Zoho Campaigns, we recommend our users don't send a huge volume of email from a new sender domain. This is because the new sender domain will have no reputation with mailbox service providers. Also, mailbox providers consider emails from a new sender domain that has no reputation to be suspicious. When our users decide to use a new sender domain, we recommend them to warm up the sender domain first. Users can warm up the sender domain by sending a few emails to start and slowly increasing the email volume based on the response the sent emails receive.

Click here to learn more about warming up your sender domain.

IP address

At Zoho Campaigns, our users can choose between using a shared IP address or a dedicated IP address based on their business requirements. The reputation of an IP address is a crucial factor that mailbox providers assess before making inbox decisions. Hence, we recommend our users ensure that their IP address always earns a positive reputation from mailbox providers and anti-spam services.

Using a dedicated IP address

When businesses migrate from a different email marketing service provider to Zoho Campaigns and opt for a dedicated IP address, we always urge them to warm it up first. This is because a dedicated IP address will have no reputation with mailbox providers and anti-spam services. We recommend businesses send a few emails first and slowly increase the email volume based on the response the sent emails receive.

Anti-spam engine

At Zoho Campaigns, we've a powerful anti-spam engine that helps us identify and neutralize spam. All the campaigns created by our users will be subjected to a stringent review process before we approve it. Our anti-spam engine, powered by state-of-the-art spam filters and algorithms, scans the sender domain, email content, and the URLs used in a campaign to identify patterns that point to spam. When our engine identifies spam, it won't approve the campaign and will block the user's account.

Contact management

Mailing lists are the fundamental blocks on which email marketing is built. Hence, we always recommend our users grow their mailing lists organically and maintain quality mailing lists. The success of a campaign depends on the quality of the mailing list. If the quality is poor, the emails you send may bounce, receive spam markings, unsubscribes, or even complaints. To grow a healthy mailing list, we urge marketers to use the double opt-in technique as it will eliminate the possibility of invalid email addresses and spam traps entering the mailing list.

Once a contact enters the mailing list, we recommend marketers segment the list and group contacts based on their needs, interests, and demographic factors like age, gender, etc. After segmenting the mailing lists, you can use the target marketing strategy to offer content relevant to your contact's needs and interests. As you grow your mailing lists, we recommend you identify inactive contacts and win them back by sending re-engagement campaigns.

The best way to keep your mailing list active and buzzing is by keeping your contacts engaged and by cleaning your mailing list every six months to remove dormant contacts.

Factors that affect deliverability

Now that we learned about the major components of email infrastructure, let's focus on factors that impinge email deliverability.

Email bounce

When sent emails can't be delivered, it is considered to be an email bounce, an issue that marketers face frequently. Though an email bounce sounds simple, it seriously affects deliverability. There are two types of email bounces.

Soft bounce

A soft bounce is a temporary delivery failure that occurs when the recipient's mailbox is full, when the receiving server is down, etc. When emails soft bounce, the server retries to deliver the email within the next 72 hours. If an email soft bounces three times, it will be classified as a hard bounce.

Hard bounce

When there is a permanent delivery failure, it is considered to be a hard bounce. Common reasons for hard bounces are an invalid recipient address, invalid domain, etc. Hard bounces will seriously damage the reputation of the sender domain and IP address. A rise in the hard bounce rate may get your sender domain and IP address blacklisted.
The reason for an email bounce is poor mailing list management practices. Hence, we urge our users to grow their mailing list organically and prune it every six months.

Click here to learn more about email bounce.

Spam markings

Your contacts mark your emails as spam when they feel that the content offered is irrelevant to their needs and interests. Spam markings are negative signals that mailbox providers and anti-spam services look out for. Whenever recipients mark an email as spam, it will incur a negative reputation for the sender domain and IP address. Also, mailbox providers may assume that the recipients are not interested in the emails from the sender and may deny inbox placement for future emails.


Contacts hit the unsubscribe button when they feel that they are not offered content for which they had signed up. Unsubscribes are negative signals that indicate that contacts are not happy with either the content you offer or your sending practices. Mailbox providers and anti-spam services consider email engagement before making inbox decisions. Whenever a contact unsubscribes, it will incur a negative reputation for the sender domain and IP address. If a lot of your contacts unsubscribe over a period, mailbox providers may not offer inbox placement for your future campaigns.


An email campaign can receive complaints either directly or through a feedback loop.

Direct complaint

When email recipients directly contact us and submit a complaint, it is a direct compliant. Whenever we receive direct complaints, we perform a grass root level analysis to understand what went wrong. If the complaint is found to be valid, we'll block the user's account and ask them to offer a detailed explanation.

Feedback loop

When an email recipient marks your email as spam, the mailbox provider will inform the business if they had subscribed to the feedback service. Whenever a business receives a notification about spam markings via a feedback loop, we'll offer best practices and suggest the business follow them. If the next campaign of the business also receives spam markings, we'll block the account and ask the business to offer a detailed explanation. We'll reinstate the account only if the explanation is valid.

Best practices to maximize deliverability

Apart from your sender domain, IP address, and mailing lists, your sending practices will also hugely impact your campaign's performance. The best way to hit your conversion goals is by adopting these hygienic practices:
  1. Craft a campaign with a compelling subject line and a pre-header
  2. Offer content relevant to your contact's needs and interests
  3. Don't use spam phrases in the email content
  4. Use 40% images and 60% text in your campaigns
  5. Have an email footer
  6. A/B test your campaigns
  7. Analyze the recipient's time zone before sending your campaign
  8. Don't send a huge volume of emails without warming up the sender domain and IP address
  9. After sending a campaign, monitor the open rate, click rate, bounce rate, and conversions
  10. Reward your active contacts with discounts on their next purchase
  11. Win back inactive contacts by sending re-engagement emails
  12. Clean your mailing lists every six months

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