If you’ve ever sent an important email to a customer, only to discover several days later that it ended up in their spam folder, you’ll know just how frustrating it can be. It’s particularly annoying when you’re sending something completely legitimate, such as a quotation or invoice, and the recipient assumes you haven’t bothered replying to them. Unfortunately, email spam filtering has become increasingly sophisticated over the years, and while this is generally a good thing for those of us who don’t particularly enjoy receiving hundreds of emails about dubious pharmaceutical products, it can occasionally cause problems for perfectly legitimate businesses.
Having worked with various email marketing platforms and business email systems over the years, I’ve come across quite a few situations where companies have struggled to get their emails delivered properly. Sometimes the problem is relatively straightforward, such as an incorrectly configured email server, but in other cases it can be considerably more difficult to identify. The important thing to understand is that your emails aren’t necessarily being marked as spam because of something you’ve written in them, and fixing the problem can involve a little more than simply removing suspicious words from your subject lines.
How Do Spam Filters Actually Work?
When you send an email, the recipient’s email provider doesn’t simply accept it and place it directly into their inbox. Instead, services such as Gmail, Outlook and Microsoft 365 use various systems to determine whether the message is legitimate, potentially unwanted or outright malicious. These systems examine numerous factors, including the reputation of the sending server, whether the email has been properly authenticated, the content of the message and how recipients have previously interacted with emails from the same sender.
For example, if thousands of people regularly receive emails from your domain and immediately mark them as spam, there’s a reasonable chance that future messages will be treated with suspicion. Conversely, if people regularly open, reply to and otherwise interact positively with your emails, that’s generally a much healthier position to be in. However, the precise methods used by email providers aren’t publicly disclosed, meaning there’s no guaranteed way to ensure that every message reaches somebody’s inbox.
It’s also worth distinguishing between emails being rejected completely and those being delivered to a spam folder. If a receiving server rejects a message, you’ll often receive an error or non-delivery report explaining what happened, whereas a message placed in the spam folder might appear to have been delivered perfectly successfully from your perspective.
Have You Configured SPF, DKIM and DMARC?
One of the first things I’d investigate is whether your domain’s email authentication has been configured correctly. There are three main technologies involved here, called SPF, DKIM and DMARC, which help receiving email servers establish whether messages claiming to originate from your domain are actually legitimate.
SPF, or Sender Policy Framework, allows you to specify which servers are authorised to send emails on behalf of your domain. DKIM, or DomainKeys Identified Mail, uses a digital signature to help verify that an email was authorised by the domain responsible for signing it and hasn’t been modified in certain ways since being sent. DMARC builds on these technologies by allowing domain owners to specify how receiving servers should handle messages that fail authentication and alignment checks.
Although these might sound rather complicated, they’re generally configured through DNS records associated with your domain name, and most reputable email providers supply instructions explaining how to set them up. However, things can become more complicated if your business uses several different systems to send emails, such as Microsoft 365 for normal correspondence, Mailchimp for marketing and a website that sends automated enquiry notifications.
If one of those services hasn’t been configured correctly, you might find that emails sent through Outlook are delivered successfully while messages generated by your website regularly disappear into spam folders. This is why I’d recommend checking all the systems sending emails using your domain rather than assuming that everything is working simply because your everyday emails are being delivered.
Could Your Email Server Have a Bad Reputation?
Another important factor is the reputation of the IP address being used to send your emails. This can be particularly relevant if you’re using inexpensive web hosting that also provides email services, as your messages might be sent through a server shared with numerous other customers.
If somebody else using that server has been sending large quantities of spam, the server’s IP address could develop a poor reputation or appear on one of the blocklists used by email providers. Unfortunately, this means your perfectly legitimate emails might encounter delivery problems through no direct fault of your own.
You can check whether an IP address appears on various email blocklists using services such as MXToolbox, although it’s worth remembering that appearing on a particular list doesn’t automatically mean every email provider will reject your messages.
Personally, I’d generally recommend using a reputable business email service such as Microsoft 365 or Google Workspace rather than relying on the basic email facilities included with particularly cheap website hosting packages. That doesn’t guarantee perfect deliverability, but it removes some of the potential problems associated with poorly maintained email infrastructure.
Are You Sending Too Many Emails?
If you’re experiencing problems with marketing emails rather than ordinary business correspondence, another possibility is that you’re sending too many messages to people who aren’t particularly interested in receiving them.
Let’s say you’ve accumulated a mailing list containing several thousand email addresses over the last decade, but haven’t contacted most of those people for several years. Suddenly sending everybody a promotional newsletter might sound like a reasonable way to generate additional business, but it could also result in a substantial number of bounced messages, unsubscribes and spam complaints.
Email providers pay attention to this sort of behaviour, and a sudden increase in sending volume can also attract additional scrutiny, particularly if your domain doesn’t have an established history of sending large campaigns.
I’d recommend regularly removing invalid addresses, reviewing contacts who haven’t engaged with your emails for a long time and making sure you’re only contacting people who have a legitimate reason to hear from you. For UK businesses, you’ll also need to consider GDPR and the Privacy and Electronic Communications Regulations, particularly when sending unsolicited marketing emails.
Using a dedicated email marketing platform such as Mailchimp can make managing these requirements considerably easier than attempting to send thousands of messages directly through Outlook.
Does the Content of Your Email Matter?
Of course, what you actually write in your emails can also influence whether they’re identified as spam, although I think there’s a tendency to exaggerate the importance of individual words and phrases.
You might have heard that using words such as ‘free’, ‘discount’ or ‘special offer’ will automatically result in your email being sent to the spam folder, but modern spam filters are considerably more sophisticated than that. They generally examine the overall characteristics of a message rather than simply looking for a handful of forbidden words.
However, I’d still avoid misleading subject lines, excessive capitalisation and emails consisting almost entirely of promotional images. It’s also worth checking that any links point to legitimate websites and that your emails contain clear information identifying your business.
For marketing emails, providing a straightforward unsubscribe option is particularly important. If somebody no longer wants to hear from you, it’s considerably better for them to unsubscribe than to repeatedly mark your messages as spam.
What Should You Do If Your Emails Keep Going into Spam?
Personally, I’d start by establishing whether the problem affects all your emails or only particular types of messages. If ordinary Outlook emails are being delivered successfully but automated website notifications aren’t, that suggests a rather different problem from every message sent by your company ending up in spam.
Next, I’d check your SPF, DKIM and DMARC configuration, examine the headers of an affected email to see whether authentication checks are passing, and investigate whether your sending IP address has developed a poor reputation. If you’re sending marketing campaigns, I’d also review your mailing list and recent engagement figures.
It’s worth remembering that being able to send an email doesn’t necessarily mean the recipient’s email provider is going to trust it. Proper email authentication, a good sending reputation and sensible mailing practices are all important, particularly when businesses depend so heavily on email for everyday communications.
Ultimately, there’s no magic setting that will guarantee your emails always arrive in somebody’s inbox, but there are plenty of things you can do to improve your chances. Given the potential consequences of customers missing important quotations, enquiries or invoices, I’d suggest it’s worth spending a little time making sure everything is configured properly rather than simply asking people to check their spam folders whenever you send them something.