Clients Not Receiving Emails from You? Time to Switch to an SMTP Provider

Over the past couple of months, you may have noticed a sudden change in your email marketing. Overnight, your emails have stopped reaching your clients. You might have gotten error messages explaining that the recipient provider failed to authenticate the sending email server, and so the email was rejected.

Unfortunately, this isn’t a glitch or some sort of mistake. Major email providers like Google and Yahoo have banded together to demand more stringent identity checks to determine that the domain sending the email is who it claims to be. The reason? To combat the rising tide of email spoofing and phishing scams. Verification technologies that were once recommended are now required if you want your messaging to reach your customers. 

In this article, the digital marketing experts at SteadyRain are breaking down how email authentication has changed, what new steps are required, and how to move forward so your clients can start receiving emails from you again.

Why Did Email Providers Change What Emails They Accept?

A frequent question we’ve heard from our clients lately is why the sudden change? Why are email providers suddenly requiring all these extra security measures to verify we are who we say we are?

It actually stems from the rising volume of phishing emails and email spoofing. A phishing attack is a type of social engineering campaign where a malicious actor attempts to trick someone into divulging their credentials or other personal information. This is often done by sending an email posing as another trusted person, business, or organization. Sometimes attackers even pose as government agencies, threatening legal action if you don’t give in to their demands!

There are increasing reports that some phishers have perfected this art, sending emails from domains and senders that look just like their real counterparts. This is done through a process called email spoofing. This process involves threat actors forging the email header so that email providers display the sender address as a trusted organization, co-worker, friend, or even family member. Most users accept email headers as they are, failing to investigate them further, which usually reveals that the header has been faked.

To stop this worrying practice, email providers have begun relying on multiple layers of authentication to prove that an email sender is who they say they are and has the authority to send emails from a specific domain.

Current Email Authentication Checks

As of 2025, many email providers are requiring email senders to prove who they say they are using a network of different authentication technologies. These technologies interact through a Simple Mail Transfer Protocol (SMTP) provider to check DNS settings.

These three checks are:

• Sender Policy Framework (SPF)
• DomainKeys Identified Mail (DKIM)
• Domain-based Message Authentication Reporting and Conformance (DMARC)

Now, we know that to most people, those are a lot of funny-sounding acronyms that don’t make a whole lot of sense, so let's break each one down.

What is SMTP and How Does It Work?

Simple Mail Transfer Protocol, or SMTP, has been around for as long as email has. It’s essentially the internet protocol for sending digital mail and can be broken down into four main parts:

• Client to server
• Server to server
• Digital routing
• Delivery

When an email is first sent, it moves from your email client (Gmail, Outlook, etc.) to a specialized server for outgoing mail. The outgoing mail server communicates with other additional email servers and determines who the email is being sent from, who its intended recipient is, and where the recipient’s email inbox is located. The email is then routed to the recipient’s inbox, where it sits after delivery.

It’s important to note that SMTP is a standard protocol for sending email, not necessarily receiving email. SMTP also doesn’t use a lot of security measures or authentication checks on its own, which is why email providers are now beginning to require those extra steps in order for emails to be received.

What is a Sender Policy Framework (SPF)?

Imagine a big party that is so exclusive, bouncers out front check a list before letting you in to see if you were invited and deny you entry if you weren’t. SPFs sort of work like that, except the party is your email inbox, and the guest list is a list of email servers that are authorized to send emails on a verified domain’s behalf.

Receiving servers check for this list to determine whether a specific SMTP server is allowed to send emails claiming to be from a domain. If the check fails, the email is likely to be flagged as spam and may even be quarantined or fail to send.

For this to work, you need to add certain files to your website’s DNS record to let email providers know which SMTP servers are okay to send emails on your behalf.

What is DomainKeys Identified Mail (DKIM)?

DKIM provides a signature of authentication that tells email providers the sender is who they say they are. DKIM relies on using SMTP servers to sign each outgoing email with a private digital signature. Receiving servers can then check your DNS records for a publicly available key that can be used to read the email signature. If the key properly unlocks the private signature, it serves as an indicator that the email is coming from the domain it says it’s coming from.

Like SFP, this method requires editing your DNS settings to allow it to function properly.

What is Domain-based Message Authentication Reporting and Conformance (DMARC)?

DMARC uses both SFP and DKIM to provide an extra layer of protection and let receiving email servers know the email is most likely coming from the domain it says it's coming from. This method protects both email recipients and legitimate domains that may experience reputational harm if threat actors start using their domain name to send malicious emails.

DMARC will check the SFP and DKIM against each other in the DNS files of a domain. If they don’t match up, the DMARC protocol informs recipient servers on how to treat the email: Quarantine or block. This protocol is contained within a .txt file uploaded to a website's DNS.

Some major email providers, like Gmail, actually require senders to utilize DMARC if they send more than 5,000 emails a day.

How Do These Changes Impact Your Business?

Now to answer the most important question: How will this impact you? There are a number of things to keep in mind.

First, if you’re still using localhost to send your emails, you’re going to need to switch to an SMTP server. Localhost doesn’t allow the same sorts of required authentication checks that SMTP servers can integrate with, so there’s a high probability that most email services will simply stop accepting your emails. If you happen to be using certain email providers like Gmail to send your emails, you may even incur penalties for sending large amounts of mail flagged as spam.

Second, even if you’re already set up on an SMTP server but you’re not utilizing a SMTP provider service that allows you to register the required authentication protocols, your emails still won’t be able to reach your clients. At the very least, most email providers require some form of sender authentication now, with some of the bigger ones taking it a step further and requiring DMARC, the most advanced form of sender authentication.

Third, if you haven’t already set up SFP, DKIM, and DMARC within your DNS settings, you’re going to need to spend some time doing that. For those who’ve never done this before, it can seem highly technical and a little intimidating. However, SteadyRain has a solution to make it easy.

Send Emails with Confidence with SteadyRain's SMTP Solutions

We know from experience that a lot of time and effort goes into crafting the perfect marketing email. There’s no greater slap in the face than to have all that effort go to waste because the rules for sending email have changed.

However, the savvy marketer learns to embrace and adapt to changes in industry technologies and trends. That’s why SteadyRain is fully recommending moving email sending operations over to an SMTP server backed by an SMTP service. SteadyRain uses SMTP2GO, an SMTP provider that makes setting up email domain authentication practices easy.

First, we create your SMTP account. Then, we upload the required files to your DNS to allow authentication checks to work, ensuring you can start hitting the send button with confidence again.

Tired of bounced emails? Speak to a SteadyRain digital marketing expert today, and let’s get those finely-crafted marketing emails back where they belong: In front of your loyal customers.

Improve Your Email Open Rates