A business sends a carefully designed newsletter, a quotation to a new client or order confirmations to customers, and many of those emails quietly land in spam or promotions folders, or are rejected entirely. Open rates drop, clients say they never received the proposal, and nobody knows why. This is an email deliverability problem, and it has become more common as major email providers tightened their rules for senders.
The good news: most causes are identifiable and fixable.
How inbox providers decide
Gmail, Outlook, Yahoo and other providers evaluate every incoming email using many signals: whether the sender is authenticated, the reputation of the sending domain and servers, how recipients interact with previous emails, complaint rates, list quality and content patterns. No single factor guarantees the inbox, but a few problems reliably push emails to spam.
1. Authentication: SPF, DKIM and DMARC
These DNS records prove that emails claiming to come from your domain are really authorised by you. Missing or broken authentication is the most common technical cause of spam placement.
- SPF lists which servers and services are allowed to send email for your domain, such as your email host and your newsletter platform.
- DKIM adds a cryptographic signature proving the email was not altered and came from an authorised sender.
- DMARC tells receiving servers what to do when SPF or DKIM checks fail, and sends you reports.
Major providers now require authentication for bulk senders, and Gmail and Yahoo also expect bulk senders to have a DMARC policy, an easy one click unsubscribe, and low spam complaint rates. Even small senders benefit from correct setup. A common mistake is adding a new sending service, such as a CRM or newsletter tool, without updating SPF and DKIM for it.
2. Sender reputation
Your domain builds a reputation over time. Reputation suffers when emails generate complaints, bounces, spam trap hits or very low engagement.
- New domains should start with low volumes and increase gradually.
- Shared sending IPs on cheap services can be affected by other senders’ behaviour.
- Separate marketing and transactional email, for example using a subdomain for newsletters, so a marketing problem does not block invoices and password resets.
3. List quality
Poor lists destroy deliverability faster than anything else.
- Never buy email lists. They contain invalid addresses, spam traps and people who never agreed to hear from you.
- Use confirmed opt in where practical.
- Remove hard bounces immediately.
- Remove or re engage inactive subscribers who have not opened in months.
- Validate addresses at sign up to catch typos.
See first party data marketing for building quality lists.
4. Unsubscribe and complaints
If unsubscribing is hard, people click “report spam” instead, which damages reputation. Provide a clear unsubscribe link, support one click unsubscribe, and honour requests promptly. Watch complaint rates in tools such as Google Postmaster Tools.
5. Content and formatting habits
Content matters less than authentication and reputation, but some patterns hurt:
- Emails that are a single large image with little text.
- Misleading subject lines.
- Excessive links, especially shortened or mismatched links.
- Broken HTML and missing plain text versions.
- Large attachments in marketing emails.
6. Engagement
Providers notice whether recipients open, reply, move emails to the inbox, or delete without reading. Send relevant content to people who want it, segment lists, and avoid blasting everyone with every message. See email marketing for ecommerce and marketing automation for SMEs.
A quick deliverability checklist
- Check SPF, DKIM and DMARC for every service that sends email for your domain.
- Set up Google Postmaster Tools for domain reputation and spam rates.
- Separate transactional and marketing sending.
- Clean your list: bounces, inactive and invalid addresses.
- Add clear and one click unsubscribe options.
- Send test emails to different providers and check placement.
- Increase volume gradually for new domains or tools.
Transactional email for apps and websites
Order confirmations, password resets and OTP style emails must reach inboxes reliably. Use a reputable transactional email service rather than sending directly from a web server, authenticate the domain properly, and monitor bounces and failures. If you are building an application, include this in the technical plan from the start.
Diagnosing a deliverability problem, step by step
When open rates suddenly fall or clients say they never received your emails, work through this sequence rather than guessing.
- Send a test to addresses on Gmail, Outlook and Yahoo, and check which folder each lands in.
- Inspect the message headers in the received email. Look for SPF, DKIM and DMARC results marked pass or fail.
- If authentication fails, identify which sending service is not included in your DNS records, and fix those records first.
- Check domain reputation and spam rate in Google Postmaster Tools for your domain.
- Check blocklists for your sending domain and IP address using reputable lookup tools.
- Review recent changes: a new email platform, a large import of old contacts, a change in sending volume, or a campaign that generated complaints.
- Review bounce reports for patterns such as many invalid addresses from one source.
- Fix causes, then send only to your most engaged contacts for a few weeks while reputation recovers.
Common DNS setup mistakes
| Mistake | Result | Fix |
|---|---|---|
| Two separate SPF records for one domain | SPF fails for everything | Merge into one SPF record listing all senders |
| New newsletter tool not added to SPF or DKIM | Campaign emails fail authentication | Add the provider’s records as instructed |
| SPF record includes too many lookups | SPF evaluation errors | Remove unused services and simplify |
| DMARC missing entirely | Bulk senders face rejection or spam placement | Start with a monitoring policy, then tighten |
| DKIM keys never rotated after provider change | Signatures fail or point to old services | Publish current keys, remove obsolete ones |
| Website contact form sends as your domain from the web server | Form notifications and replies go to spam | Send through an authenticated email service |
That last row is extremely common on WordPress sites in Pakistan, where contact form notifications silently land in spam and enquiries are missed for weeks. Using an SMTP plugin connected to a proper email service usually fixes it.
A safe DMARC rollout
DMARC policies tell receivers what to do with emails that fail authentication. Moving too quickly to a strict policy can block your own legitimate emails if some sending service was forgotten.
- Start with monitoring: a policy that only requests reports, so nothing is blocked.
- Read the reports for a few weeks to find every service sending as your domain, including CRMs, invoicing tools, website forms and support desks.
- Fix authentication for each legitimate service.
- Move to quarantine, which sends failing messages to spam.
- Move to reject once you are confident, which protects your domain from spoofing by scammers.
A strict DMARC policy also protects your customers. Scammers impersonating businesses by email is a real problem, and a domain with enforced DMARC is much harder to spoof.
Warming up a new domain or email platform
Sending thousands of emails from a brand new domain on the first day looks exactly like spam behaviour. Warm up gradually: start with small volumes to your most engaged recipients, people who opened or clicked recently, and increase volume over several weeks while watching bounce and complaint rates. The same applies when switching email marketing platforms or sending IPs.
Email habits that protect reputation over time
- Consistent sending schedule rather than silence for months followed by a huge blast.
- Segmented campaigns so people receive content relevant to them.
- Preference options letting subscribers choose frequency or topics instead of unsubscribing completely.
- Sunset policies that stop emailing people who have not engaged in a long time.
- Double checking links and images before sending, since broken content increases deletes and complaints.
- Recognisable sender names that match your brand, so recipients do not mark emails as spam out of confusion.
Business email accounts, not only marketing
Deliverability problems also affect everyday business email: quotations, invoices and replies to leads. Using free email addresses for business communication, shared accounts sending huge numbers of messages, or attachments that trigger security filters can all cause important emails to be missed. A professional email service on your own domain with proper authentication is a basic requirement for any business sending proposals or invoices. See website security checklist for businesses.
Frequently asked questions
Why do my emails reach Gmail spam but not Outlook?
Providers use different filters and reputation data. Check authentication first, then reputation and engagement for that provider.
How long does it take to fix a damaged reputation?
After fixing authentication and list problems, reputation typically improves over weeks of consistent, well targeted sending.
Do WhatsApp and SMS replace email for business?
They complement it. Many customers prefer WhatsApp for quick updates, but invoices, contracts, receipts and B2B communication still rely heavily on email reaching the inbox.
How often should we clean our email list?
Remove hard bounces automatically after every send, and review inactive subscribers every few months with a re engagement message before removing them.
The bottom line
Emails go to spam mostly because of missing authentication, poor list quality, complaints and weak engagement. Fix SPF, DKIM and DMARC, clean your lists, make unsubscribing easy and send relevant messages consistently.
Our digital marketing team can help audit email setup and campaigns.