8 tips for great email reputation and maximum deliverability – Part I


Email sending and deliverability is all about domain/IP reputation. If your domain - that you use for sending - has a good reputation with an ISP, your emails will arrive almost constantly in your recipient's inbox. In case of a bad reputation, you will notice a drop in delivery speed and your emails can arrive in the spam box. In worst case, you can get blacklisted. As ISPs consider you as "not trustworthy", they limit the number of emails per minute you can send to them and scan the content more strictly. Fortunately, you can influence your reputation in a positive sense by following our guidelines.

1. Get to the inbox

The image below (provided by Return Path) gives a good overview of the complexity of the process.


As you notice, a lot of factors influence your reputation and deliverability. Moreover, reputation is not a snapshot taken at one single moment in time. It is a continuous effort that should be constantly monitored and managed.

2. Identify yourself

Authentication allows the receiver of an email and the ISP to confirm the identity of the sender. If the identity of the sender can't be authenticated, ISPs may reject the message or put it through additional filters to determine whether it should be delivered or not. Without authentication, your chances of being filtered by major ISPs are greatly increased.

Email authentication is important because it addresses one of the main security problems inherent to the email sending technology. Authentication is integral to prevent phishing and other fraud. As a legitimate business, authentication is not optional. It is essential to securing your brand and online reputation.

Authentication can be realized with the setup of SPF and DKIM records in the Domain Name System (DNS):


The Sender Policy Framework (SPF) is an email validation system designed to prevent spam by detecting email spoofing, a common vulnerability, through verification of sender IP addresses. SPF allows administrators to specify which mail servers are permitted to send email on behalf of a given domain. Therefore, they create a specific SPF record (or TXT record) in the DNS. Email exchangers use the DNS to check if email from a given domain is being sent by a host sanctioned by that domain's administrators.

The purpose of an SPF record is to prevent spammers from sending messages with forged From addresses at your domain. Recipients can refer to the SPF record to determine whether a message claiming to be from your domain comes from an authorized mail server. If your domain does not have an SPF record, some recipient domains may reject messages from your users because they cannot validate that the messages come from an authorized mail server. Therefore, we recommend that you create a SPF record for your domain.


Domain Keys Identified Mail (DKIM) is a method for associating a domain name to an email message. It allows a person or organization to claim responsibility for the message. The association is set up by means of a digital signature which can be validated by recipients. Responsibility is claimed by a signer, which acts independently of the message's author or recipient, by adding a DKIM-Signature field to the message's header.

As mentioned above, spammers can forge the From address of email messages so that the spam appears to come from a user in your domain. To help prevent this sort of abuse, you can add a DKIM Signature field to the header of email messages sent from your domain.

Recipients can check the domain signature to verify that the message really comes from your domain and that it has not been changed along the way. Prominent ESPs implementing DKIM include Yahoo, Hotmail, Gmail, AOL and Fastmail. Any email from these organizations should carry a DKIM signature.

Email authentication, like SPF and DKIM, will not solve your deliverability problems. Validating a domain only authenticates the identity of the sender. It does not speak of the content of the email message. However, authentication will make it harder for your domains to be forged and is critical to your brand reputation and subscriber trust.

3. Feedback loops

A feedback loop is an inter-organizational system by which an ESP forwards complaints from their mailbox owners to the sender's organization. These complaints are registered when a user clicks the "Report spam" button in their email client. Consequently, the sender receives these complaints and processes them according to its company policy. In most cases, the best way to deal with spam complaints is unsubscribing the user and registering the complaint in a campaign report. This is a fairly typical way of how feedback loop complaints are dealt with.

If you choose to use a specific ESP, you can check with them as to whether they are integrated with feedback loops. While it might seem risky to open yourself up to such direct complaints, it is better to handle them right away than having to find out that you have been blacklisted later on. Follow this link for a list of the major feedback loops. Hotmail offers a feedback loop under the name of JMRP (Junk Mail Reporting Program) for instance.

4. List-unsubscribe

The List-Unsubscribe header is an optional block of text that email publishers and marketers can include in the header part of their emails. Recipients do not see the header itself. Instead, they see an unsubscribe button that can be clicked when they would like to automatically stop future messages.

Including a List-Unsubscribe header in your emails will reduce complaints, improve deliverability and improve the experience of your subscribers. One obvious benefit is that recipients will be able to easily and reliably unsubscribe if they want to, as opposed to frustrated users who do not find the actual opt-out link and are likely to hit the "Report Spam" button or complain in some other way, hurting your sender reputation in the end.

Stay tuned for more tips and best practices to improve email reputation and deliverability!