Audit Your Email Delivery

Audit Your Email Delivery

Audit Your Email Delivery

No matter how powerful email marketing software you use, if your email delivery has problems, you will not be able to get significant results from your email marketing campaigns.

Email delivery is not a one-time set and forget process. You need to keep an eye on your email delivery infrastructure, monitor its health and take immediate action when there’s a problem with it.

First of all, let’s make sure we are on the same page. What’s email deliverability? Email deliverability is the number of emails that have been sent by your mail servers and received successfully by recipient mail servers.

Do not confuse email delivery rate with inbox/spam folder delivery rate. It’s a different story. On this article, we will explain to you how to make sure that your email delivery servers are in good standing and emails they send are accepted by the majority of your audience mail servers.

Email is the highest ROI marketing channel, even in 2022. And do not forget that your competitors are also using email marketing to reach out your target audience and make more sales.

If you build and sustain a healthy email delivery infrastructure, you will get ahead of your competition, reach out to a bigger audience, sell more, get a bigger market share.

Audit Steps

A healthy email delivery infrastructure audit consists of;

  • Email server setup
  • Audience and email campaigns
  • Authentication
  • Reputation

Email Server Setup

A and PTR Setup

Your email server has IP addresses. Each one of these IP addresses (we call them as “sender IP address”) must have a unique PTR record. For example, if your sender IP address is, it must have a PTR record such as Now, let’s make sure that PTR domain also resolves ot the sender IP address.

On Linux/Mac, you can do the check using this command sequence:

% dig +short -x

% dig +short

As you can see above, the sender IP resolves to the PTR, and the PTR resolves to the sender IP address ✅.

Audience and Email Campaigns

No matter how perfect your email delivery infrastructure is, if your audience or email campaigns are causing problems, you will lose the good standing of your email delivery infrastructure quickly.


Make sure that your entire audience has been collected through double opt-in forms. If you have audience members collected in a single opt-in or if you have added new audience members from third party sources, you have bomb in the house. Potential hard bounces, spam traps, and spam complaints will cause you a big trouble. Use or similar email list verification service to get rid of these risky email addresses as much as you can.

Also, consider segmenting your audience into two different segments;

  • People who have opened or clicked in the last 30 days → ACTIVE
  • People who haven’t opened or clicked in the last 30 days → INACTIVE
You may also consider using different email delivery servers for each one of these audience segments. In this way, you avoid inactive audience members to lower the delivery reputation of your primary delivery server.

Email Campaigns

Your email campaign content must be recipient friendly. Otherwise, it will cause spikes on opt-outs, and most importantly spam complaints.

First of all, make sure that you are not sending spam emails. Also make sure that;

  • You have segmented your audience and sending relevant content to the correct audience segment. Always, send the right message to the right person.
  • Check and make sure that links inside your emails are working and they don’t have multiple redirections (such as affiliate links with multi-hops).
  • Make sure that email personalization has been done correctly and you don’t send emails with personalization tags unprocessed.
  • If you are sending a long email content, make sure that the sender information and opt-out link exists at the top of your email. Gmail and similar ISPs clip long emails and this will cause your opt-out link not to be displayed.
  • Make sure that you have added an instruction about how to whitelist/add to contact your sender information. If recipients find your emails useful/interesting, they will add you to their contact list and this will boost your email delivery reputation.
  • Always use relevant, compelling and not-spammy email subject lines. Never try to trick recipients with catchy subject lines that do not make any sense.
  • Always send your emails with a from (or reply-to) email address that can receive emails. Getting a reply from your audience is the best thing that can happen in your email marketing campaigns.
  • Use or similar services to test your email content, links, images, image URL’s and many other email components and make sure that everything is okay.

Email Delivery Volume

If you are sending let’s say 10,000 emails per week to your audience, but then suddenly increase your weekly delivery volume to 100,000, this is a problem. Most ISPs will detect this spike in email delivery volume and throttle your emails. Your emails will be rejected by the recipient MX servers and you will not be able to delivery any emails.

Error: "421 4.7.0 [TSS04] Messages from temporarily deferred due to unexpected volume or user complaints -; see" while connected from ( to (

Make sure that you increase the volume slowly over time. Sending more is always a problem for your email delivery infrastructure.

Email Delivery Frequency

Just like email delivery volume, frequency is also important. What’s email delivery frequency? It’s the number of emails that each one of your recipient receives over a time.

It’s important to segment audience into “Active” and “Inactive” but also, it’s important to keep the number of emails you send to your audience as low as possible. If you send too many emails to your recipients in a short period of time, this will cause opt-outs and spam complaints.

Avoid sending many emails in a very short period of time to your subscribers. This will cause spam complaints and you will lose your active audience members.


There are three “must-have” email authentication methods you must setup and make sure that properly configured:

  • SPF (Sender Policy Framework)
  • DKIM (Domain Keys Identified Mail)
  • DMARC (Domain-Based Message Authentication)


Make sure that your sender IP addresses are authorized to send emails on behalf of your sender domains. If your sender IP address is and your sender domain is, you must add an SPF record to the DNS control panel of just like; TXT "v=spf1 ip4: -all"

If you have an existing SPF record, simply modify it. Otherwise, create a new one.


DKIM authentication uses public-key cryptography to sign email with sender’s private key during the SMTP email delivery. Recipient email servers use a public key published to the DKIM's domain to verify the source of the message, and that the parts of the message included in the DKIM signature haven't changed since the message was signed.

To sign your emails with DKIM, private and public keys must be created. The private key will be used to sign the email and the public key will be used to verify the email integrity.

Your email server must be configured properly to sign the emails.


DMARC uses SPF and DKIM to determine the authenticity of an email.

DMARC is very useful to prevent malicious emails such as domain spoofing and phishing emails.

You can use MXToolbox’s DMARC generator to generate your DMARC records.

If you have an incorrect setup SPF or DKIM record, the DMARC policy will cause your emails to be rejected by the recipient servers. Make sure that SPF, and DKIM are set properly.


Your sender reputation is based on the combination of the sender IP address reputation and sender domain reputation. Your sender reputation is affected from the number of hard bounces occur on your email deliveries, spam complaints, spam trap hits, opt-out rates, and engagement rates (open, click, reply, archive, delete, etc.).

Email delivery reputation building takes time, never try shortcuts. Please the long-term game in order to succeed with your email delivery and sustain the a long-lasting email delivery reputation.

If you are sending low volume email, you may consider using a shared IP address. Using a shared IP address for email delivery will help you to inherit the reputation of the already established reputation. However, be careful about the shared IP address you will be using. If it has a bad reputation, you will be affected.

Based on your audience ISP breakdown, you may consider using ISP postmaster dashboard such as Google Postmaster and Microsoft SNDS.

In addition to this, keep an eye blacklist status of your sender domains and IP addresses. You can use or similar services to monitor the health of your senders regularly and get alerts when there’s a problem.


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