Email authentication is the process of verifying the identity of an email sender and ensuring that the email has not been tampered with during transmission. As a developer, it is essential to understand the different email authentication methods and implement them correctly to prevent email fraud and increase email deliverability. In this blog, we’ll explore the different email authentication methods and how to implement them as a developer.

Why Email Authentication is Important?

Email authentication for developers is a process that ensures emails sent from your domain are legitimate. Let’s check out the top 5 reasons to invest in these protocols-

1. Reduced Bounce Rate

Email authentication helps improve email deliverability rate by checking email addresses in the database and performing real-time tests to know if the accounts are active or dormant. It decreases the probability of your emails landing in the desired recipients’ inboxes.

2. Accurate Insights

As your mailing list gets cleared on using the tools, you get reliable and actionable analysis of your marketing campaigns.

3. Saves Money

You’ve to spend money on storing emails and managing a database to send messages. As developers implement the protocols in their applications, the email list gets cleared, and the size of your database decreases, which saves money.

4.High ROI

A detailed understanding of email authentication for developers helps reduce the bounce-back rate, which consequently gives you better ROI. Email bounces mean a waste of sums invested in email marketing.

5. Reduction in Spam Complaints from Customers and Prospects

In 2022, as many as 49% of emails were marked as spam globally. Ideally, the spam complaints have to be less than five for every 5000 email messages sent from an account. The email verification process flags spam messages and notifies you so that you can take timely action to control this.

What is SPF?

Email authentication for developers starts with the understanding and implementation of SPF or Sender Policy Framework. This protocol works by asking you to create and update a list of servers permitted to send emails using your domain name. The list is added to the DNS server from where the receivers’ servers verify if a sender’s server is part of the list or not. All emails sent from IP addresses out of the list fail SPF email authentication. The best C# developers understand the importance of SPF email authentication and can easily implement it to ensure secure and reliable email communication.

All this requires an SPF record which is a TXT record that lets administrators enter arbitrary texts into DNS.

What are SPF Record Tags?

Tag	Purpose
Version (v)	It represents the SPF versions and should be the first tag in an SPF record.
mx	The mx record specifies which server is responsible for accepting emails on behalf of the domain. It has an IP address and a priority value for each server for accepting messages.
a	It’s used when you query for an A or AAAA record in a domain having the sender’s IP address.
ptr	Ptr tag uses the reverse hostname or subdomain of the sending IP address to specify the target domain name. It’s used only if there’s one MX record. This tag is NOT recommended to be used per RFC 7208.
ip4	It tells an IPv4 IP address or IP CIDR Range that is allowed to send mail from your domain.
ip6	It tells an IPv6 IP address or IP CIDR Range permitted to send emails from your domain
include	By using this tag, app developers can include another domain or subdomain’s entire SPF record. You need to use it when a third-party service sends emails on your behalf.
exists	This tag performs an A record lookup to verify if one exists. You see the ‘pass’ results if it’s there.
all	This tag is added at the end of an SPF TXT record. It specifies instructions on how your emails should be treated if there isn’t a match to your SPF record. There are 3 common options used that allow a sender to tell the user to reject mail that does match the record (-all), treat mail as suspicious (~all), and make a neutral recommendation (?all) which leaves it up to the recipient.

Limitations and Challenges of SPF

SPF isn’t sufficient to combat all types of phishing and spamming attacks attempted in your company’s name. So, while learning about email authentication for developers, you need to focus on understanding the limitations of SPF limitations.

There’s a 10-lookup limit restriction that’s implemented to avoid overloading a DNS server’s validator resources like bandwidth and CPU. Once the limit is reached, your mail server won’t process further, and you’ll come across an SPF Permerror. Exceeding this limit causes email deliverability issues by decreasing the probability of emails landing in the desired recipients’ inboxes. You can stay within the limit by:

Removing unused services
Removing the default SPF values
Avoiding the use of ptr mechanism
Avoiding the use of mx mechanism
Using IPv6 or IPv4
Not flattening your SPF record

Another limitation is that SPF records are applied to specific Return-Path domains and not the From address. Threat actors take advantage of this cybersecurity vulnerability to execute phishing attacks by forging the From address.

What is DKIM?

DKIM stands for DomainKeys Identified Mail, a protocol that authenticates emails using the encryption method. A domain administrator adds a DKIM record to DNS and receives a pair of public and private keys. The originating email server has secret private DKIM keys, which are verified by the receiving mail server with the other half of the keypair called the public DKIM key. These DKIM signatures move with the emails and work on forwarded mail chains as well.

When DKIM alignment fails, your domain’s email deliverability rate is impacted negatively, causing emails to land in the spam folder or get rejected by the receiver’s mailbox.

What are DKIM Tags?

There are many informal elements as part of the DKIM tag cluster. These are classified as required and optional tags. We’re discussing the uses of required tags here; click here to learn about other tags in detail.

Required Tags

These tags are required for verification as recipients mailboxes reject emails without them.

v= The version tag that represents the DKIM standard being used. Its value is always set to 1.
a= This DKIM tag represents the cryptographic algorithm used for creating the signature. generally, it’s value is rsa-sha256. If your computer has reduced CPU capabilities, you can use rsa-sha1. Experts don’t encourage its use due to security vulnerabilities.
s= this tag specifies the selector record name used for finding the public key in a domain’s DNS. Domain administrators or app developers have to enter a name or a number in this field.
d= You can see the domain used with the selector record to locate public keys. It uses the same value as the domain name used by the sender.
b= This DKIM tag is used for the header’s hash data. It’s usually paired with the h= tag for drafting the DKIM signature. It’s always encoded in Base64.
bh= This required DKIM tag has the computed hash of emails whose value is a string of characters denoting a hash determined by an algorithm.
h= This tag enlists the headers seen in the signing algorithm to generate the hash in the b=tag. Its value can neither be removed nor changed.

Limitations and Challenges of DKIM

Legitimate emails sent from your domain can occasionally get rejected by mobile devices if the message is forwarded. Receiver’s server identifies them as forged messages when they read the authentication instructions.

What is DMARC?

The last leg of the understanding of email authentication for developers is learning about DMARC or Domain-based Message Authentication, Reporting, and Conformance. It works in alignment with SPF and/or DKIM results to decide how to deal with emails failing email authentication checks. You can choose to set your DMARC policy to p=none (no action is taken against the failed emails), p=quarantine (failed emails are marked as spam), or p=reject (the entry of failed emails is rejected).

You can start by setting your policy to ‘none’ to monitor if all legitimate emails are passing the verification checks. Later, you can reset it to ‘quarantine’ or ‘reject’.

What are DMARC Tags?

As a domain owner, you can specify the following DMARC tags in your DMARC record-

v: It denotes the DMARC protocol version and always has the value v=DMARC1.
pct: This tag specifies what percentage of emails are compliant with the policy mode.
p: The p tag addresses the DMARC policy mode. You can select from reject, quarantine, and none.
rua: This optional tag indicates the email address or web server where reporting organizations can send their DMARC aggregate rua data.
ruf: It tells the address to which the DMARC forensic ruf report is to be sent.
fo: it’s an optional tag that caters to the available failure/forensic reporting options domain owners can choose from.
aspf: It lets you set the SPF alignment mode. The value can be either strict(s) or relaxed(r)
adkim: It lets you set the DKIM alignment mode, the value of which can be either strict(s) or relaxed(r)
rf: This tag specifies the various formats for Forensic reporting.
ri: This optional DMARC tag has a default value of 86400, and it tells the time interval in seconds between two consecutive aggregate reports sent by the reporting organization to the domain owner.

Final Words

Email authentication for developers is critical to stay abreast of phishing and spamming attacks attempted in your name. Start by generating SPF, DKIM, and DMARC records for your official email-sending domain using our PowerToolbox.

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Ahona Rudra

Domain & Email Security Expert at PowerDMARC

Ahona is the Marketing Manager at PowerDMARC, with 5+ years of experience in writing about cybersecurity topics, specializing in domain and email security. Ahona holds a post-graduation degree in Journalism and Communications, solidifying her career in the security sector since 2019.

Email Authentication for Developers