9 Tips to Boost Your Email Deliverability
By Nick Smith
3rd September 2025
It’s easy to assume messages you send to valid email addresses will automatically be received, and hopefully opened & clicked – but this isn’t always true.
Your emails may be received by servers hosting those inboxes, yet never shown to the human beings on the other end. Instead anti-spam filters may place them in spam folders where they may not be seen, or hide them from recipients entirely.
So even if messages you send are “delivered successfully” (email delivery) how many are placed in inboxes, junk folders, or not shown at all (email deliverability) is often more crucial, and also harder to measure.
Why is email deliverability important?
The good news is in 2025 email remains the simplest, most cost-effective way to reach the largest possible business audience and probably will for the foreseeable future.
The bad news is email deliverability rates have been dropping across all industries the past few years, which means it takes more effort & expertise to achieve the results of the past.
Servers hosting email inboxes now use AI-powered algorithms to decide which emails should be graded as spam, and some of the larger email providers like Gmail & Outlook have imposed rules on using their services to send emails in bulk, making the email landscape trickier to navigate.
How can email deliverability be measured?
Most bulk email platforms & CRMs present users with stats for open & click rates when sending campaigns, but frustratingly these don’t tell the full story.
Emails marked “opened” may have been opened by servers on the other end, yet never shown to humans who own those inboxes. Emails marked “clicked” can indicate those links were checked for viruses or malware by the server itself, rather than an actual person.
A good indicator of email deliverability is how many responses, inquiries & sales an email campaign generates for you, but another way to get a better understanding is by using a deliverability testing tool like those from Mail-Tester, Glock Apps or Mailreach.
What can be done to help emails get through successfully?
Email deliverability naturally fluctuates over time, and there’s always variations between campaigns based on factors beyond your control that impact how many emails are successfully delivered to inboxes.
However there’s lots of little things you can do to stack the odds in your favour, and most fall under the category of mistakes to avoid:
- Watch out for spam keywords
One of the most common reasons your emails don’t get delivered is if they include lots of spam keywords – you can find a complete list of them here.
In an ideal world both your email’s subject line & body text contains no spam keywords whatsoever, but that’s tricky since even things like dollar symbols ($) in prices can trigger spam filters.
In reality, using a spam keyword checker like Folderly to remove as many spam keywords you feasibly can maximises your odds of successful delivery.
- Consider the email address you send from
Often overlooked, emails sent From: generic addresses like marketing@company.com.au or sales@company.com.au will have a lower chance of successful delivery than those sent from personalised emails like john@company.com.au or mary@company.com.au.
Emails sent from a domain registered to your business like person@abcbuilders.com.au or person@sydneydental.com.au will also more likely get through than those sent from free emails like Gmail, Outlook, or Yahoo because more spam gets sent from those types of email accounts, which email servers are aware of.
- Be careful with images
Email servers use algorithms to judge if incoming messages should be classified as spam, and because emails that advertise products usually have more images than those sent between co-workers the more images you include the less likely your email will be delivered.
We find the more text your email contains the more images you can safely use, with an ideal ratio being 70% text to 30% images at most. The file sizes of your images also matters with smaller being better, keeping the HTML & all images in your email under 102KB will improve deliverability. When building your emails using HTML code, every image should also have an ALT attribute defined.
- Use web safe fonts for text
Once upon a time the choice of fonts in your emails was purely stylistic, perhaps decided by whoever was paid to design your logo. Times have changed and now your choice of email fonts does affect deliverability.
We recommend using only 1-2 of these Web Safe Fonts: Arial, Helvetica, Verdana, Georgia, Times New Roman or Tahoma in any text in your emails.
For images (such as logos) you can use any fonts you like because email servers aren’t capable of “seeing” fonts used in them. If you choose not to specify which fonts your emails use then a default Web Safe Font will automatically be chosen and you’ll be fine.
- Don’t include attachments
It can be tempting to attach say a PDF price list or pamphlet to your emails, but this can be a huge mistake.
Unfortunately many scammers often attach files, which has left many people wary of opening email with attachments from senders they don’t recognise out of fear of malware or viruses.
Many emails servers automatically block email attachments so you can’t rely on your audience receiving any information they contain. Adding an attachment also makes it more likely your emails won’t be delivered, so they’re a terrible idea all round.
A far better solution is to include a Call To Action link in your email that brings those who click to your website, where they can download or simply view the information needed.
- Don’t include too many links
Call To Action buttons or links that direct recipients to your website or landing page where they can express interest & purchase are invaluable, but links should be used sparingly in emails – too many is a tell tale sign you’re sending a marketing email that will wind up in the spam folder or not delivered at all.
We recommend including no more than 1 link per 100 words of copy, and bear in mind you need a working unsubscribe link which counts the same as any other link for this point.
To maximise deliverability your email would ideally contain no more than 2 links total, including that unsubscribe link. You should also be wary of using link shorteners like Bitly as these have been proven to hurt deliverability.
- Improve reader engagement
Up until now this article must’ve read like a series of pitfalls to avoid, the good news is by improving how engaged recipients are with your emails (measured by how often they open them, click links inside them & reply to them directly) email servers will take note & deliver more of them successfully.
You can improve open rates using a Subject Line Tester to craft more enticing subject lines, and improve click rates with highly visible & carefully worded Call To Action buttons that entice them to your website.
You could also break down your list by industry, location or even job description and tailor your copy more closely to each specific audience. That requires more effort as you’d need to craft different emails for each group which would need to be scheduled to go out separately, but the results may be worth it.
- Consider how quickly you send emails
How many emails you send per day significantly impacts their odds of being delivered.
Spammers often blast out huge numbers of emails very quickly, doing similarly hurts your chances. We recommend sending no more than 1,000 emails a day, and ideally send on a consistent basis rather than increase your email volume massively on rare occasions you promote a new product or run a sale.
The ideal number of emails per day can vary depending on how specific the message is to your audience – pitching accounting software to accountants could be done faster than promoting cleaning services to multiple office-based industries, and it’s best to reach people hearing from you for the first time slower than those who’ve received your emails before.
- Email platform authentication
This one’s quite technical so it gets overlooked, but can have a huge effect on deliverability.
Email platforms like Mailchimp give you the option of authenticating your sending domain (ie. yourcompany.com.au) with settings like SPF & DKIM. This is usually done by an IT staffer or someone with a technical background, and informs email servers receiving your messages that you have authority to send emails from your domain.
Most email platforms won’t require you to complete this step to start sending, nor will they warn you that sending without a properly authenticated domain may cripple your results.
Having an expert to set this up for you or learning how to do it yourself usually pays dividends in long term results.
How do you know if making these changes is worth the effort?
The easiest way is to craft two separate emails for your next campaign – one that implements these suggestions and another that doesn’t. By splitting your contact list in half & sending each half a different email, you can then gather some evidence on whether jumping through these extra hoops is worth the trouble.
You may want to do that several times over the course of a few weeks or months for a clearer picture, but even a single test may give you all the proof you need – especially if you’ve ignored email deliverability up until now.
Many of these areas can be quite technical, so if you do have any questions or need assistance please don’t hesitate to give us a ring on 1800 961 500, we’re happy to share insights we’ve gathered in what can be a surprisingly involved aspect of marketing.