Email deliverability is the most boring-sounding problem that will absolutely destroy your newsletter if you ignore it. Creators obsess over open rates, subject line A/B tests, and content calendars. Meanwhile, a misconfigured DNS record is silently routing 30% of their sends straight to spam folders. Nobody notices until the revenue stops making sense.
This is not a rare edge case. It's endemic. And the creators who get burned worst are usually the ones who thought they'd sorted it months ago.
What 'Going to Spam' Actually Costs
Let's put a number on this. If your newsletter has 10,000 subscribers and your open rate sits at 40%, you're getting roughly 4,000 opens per send. Drop your deliverability so that 25% of emails land in spam, and suddenly you're working with 7,500 delivered emails. Your open rate doesn't fall uniformly either. The people most likely to open are often in corporate email environments with aggressive filtering. So that 40% open rate can crater to 28% or lower overnight.
For a creator monetising through sponsorships, that's not a rounding error. Sponsors pay on CPM or guaranteed open minimums. Miss those thresholds and you're either renegotiating deals or refunding advertisers. For someone charging £500 per placement at a 4,000-open guarantee, delivering 2,800 opens means a conversation nobody wants to have.
Paid subscription newsletters get hit differently. Churn goes up because readers assume you've gone quiet or lost interest. They're not checking spam folders. They just cancel.
The SPF and DKIM Confusion Is Almost Universal
Here's where most creators are quietly failing on email deliverability: they set up SPF and DKIM once, ticked the box, and haven't thought about it since. The problem is that "set up once" often means "set up incorrectly once."
SPF (Sender Policy Framework) tells receiving mail servers which IP addresses are authorised to send email on behalf of your domain. DKIM (DomainKeys Identified Mail) adds a cryptographic signature to your emails so the receiving server can verify the message wasn't tampered with in transit. Both matter. Neither is sufficient alone.
The most common SPF mistake isn't missing it entirely. It's having too many DNS lookups. SPF records have a hard limit of 10 DNS lookups during validation. Most creators don't know this exists. They add their newsletter platform, their transactional email service, Google Workspace, a CRM tool, and suddenly they're at 12 lookups. The SPF check fails. Silently. No error message arrives in your inbox to tell you this is happening.
DKIM problems tend to be subtler. The most frequent issue is key rotation. When you switch email platforms or your provider rotates their DKIM keys, the old DKIM record in your DNS becomes invalid. If nobody updated the DNS record, every email you send fails DKIM validation. Again, you won't necessarily know. Your emails still arrive for some recipients. Others filter them to spam. Your aggregate open rate drifts down by a few percentage points a week and you blame your content.
'Most deliverability problems aren't dramatic failures. They're slow leaks. The kind that seem like seasonal variation or audience fatigue until you actually check your authentication records.'
DMARC Is the Part Everyone Skips
If SPF and DKIM are the foundation, DMARC (Domain-based Message Authentication, Reporting and Conformance) is what ties them together and actually tells you when something's broken.
A DMARC policy tells receiving mail servers what to do when an email fails SPF or DKIM checks. Policy options run from none (monitor only, do nothing) to quarantine (send to spam) to reject (block entirely). Most creators who've heard of DMARC have set it to none because that felt safe. But none without actually reading the reports is pointless. You're generating data you never look at.
The genuinely useful thing about DMARC is the reporting. When you configure a rua tag with an email address, you start receiving aggregate reports from major mail providers about what they're seeing from your domain. These reports are XML files that are painful to read raw, but run them through any free DMARC report analyser and suddenly you can see exactly which sources are sending email as your domain and whether they're passing authentication.
Gmail and Yahoo made DMARC a requirement for bulk senders in early 2024. If you're sending more than 5,000 emails a day to Gmail addresses, you need a DMARC record at none minimum, with proper SPF and DKIM alignment. Plenty of newsletter creators hit that threshold without realising it. One decent viral send and you're in bulk sender territory.
Your Email Deliverability Audit Checklist
Before assuming your content is the problem, check the infrastructure. This takes about 20 minutes and costs nothing.
- Run MXToolbox on your domain. Free tool. Check your SPF record exists, has no syntax errors, and lists your current sending platforms. If you've changed ESP in the last year, the old provider might still be in there, or the new one might not be.
- Count your SPF lookups. Tools like dmarcian's SPF surveyor show exactly how many lookups your record generates. If you're over 10, you need to flatten the record. Most ESPs have documentation on how to do this.
- Verify DKIM in your ESP dashboard. Every major newsletter platform has a section where you can see DKIM status. Check it. If it says "pending" or shows an error, that's your problem.
- Check your DMARC record. If you don't have one, add a
nonepolicy today. If you have one, make sure theruatag is pointing somewhere you actually monitor. - Send a test email to mail-tester.com. It scores your email out of 10 and tells you exactly what's failing. A score below 8 means something needs fixing before your next send.
- Look at your spam complaint rate in Google Postmaster Tools. If you haven't set this up, do it now. It's free and it shows Gmail's view of your sender reputation. A complaint rate above 0.1% is a warning sign. Above 0.3% and Gmail will start throttling your delivery.
The List Hygiene Problem Nobody Talks About
Authentication fixes the infrastructure side of email deliverability. But you can have perfect SPF, DKIM, and DMARC records and still have terrible deliverability if your list is full of unengaged subscribers.
Mail providers are increasingly using engagement signals to filter email. Gmail watches whether recipients open your emails, click links, move them out of spam, or star them. If a large percentage of your list has never engaged, those addresses are dragging your sender reputation down. The inbox algorithm interprets mass non-engagement as evidence that recipients don't want your email. Which, functionally, they don't.
The counterintuitive advice here is to delete subscribers. Aggressively. Anyone who hasn't opened in 90 days and never clicked anything should be in a sunset campaign. Send them one re-engagement email. If they don't respond, remove them. A list of 5,000 engaged subscribers will outperform a list of 15,000 with 8,000 ghosts on every metric that matters, including deliverability.
This is where platforms matter. Some newsletter tools make list cleaning awkward or charge you for subscribers you're actively trying to remove. If cleaning your list costs you money, you have a platform incentive problem worth addressing separately.
Aldus builds engagement tracking into the platform specifically because deliverability depends on knowing who's actually reading, not just who subscribed six months ago.
When to Call In a Deliverability Specialist
Most deliverability problems are self-diagnosable with the checklist above. But if you've fixed authentication, cleaned your list, and your open rates are still declining, you might be dealing with a blacklisting issue or a domain reputation problem that predates your current efforts.
Check MXToolbox's blacklist checker. If your sending IP or domain appears on major blacklists like Spamhaus, that's a different category of problem. It requires delisting requests and potentially a new sending domain with a reputation warmup period.
A dedicated deliverability consultant charges anywhere from £200 to £2,000 depending on the complexity of the problem. For a creator making serious money from their newsletter, that's almost always worth it. For someone earlier in the journey, the free tools will handle 90% of what you're dealing with.
The main thing is to stop treating email deliverability as someone else's problem. Your ESP does not guarantee your emails reach inboxes. They give you the infrastructure. Whether you land in the inbox or the spam folder depends on your domain's authentication setup, your sender reputation, and your list quality. All three are yours to manage.
Most creators only start caring after a major campaign tanks. The smarter move is to check now, while everything feels fine, because the problems that hurt most are the ones you didn't see coming.