Find the evidence.
Choose the next step.
Marketing emails can go to spam because authentication is incomplete, recipients do not expect the message, or the receiving provider distrusts the sender or its links. Start by confirming what happened to the actual email. Then check authentication, audience expectations and the sending pattern before changing your campaign.
This checklist helps UK businesses investigate the cause and ask for useful help. Email Blaster provides email marketing software and a UK team you can talk to; no software or authentication record can guarantee inbox placement. Explore our email marketing software overview.
Email Blaster publishes this guide and supplies email marketing software. The examples are diagnostic suggestions, not results from a customer campaign or a promise of delivery. Mailbox-provider rules can change.
Was the message rejected, put in Spam or sorted into Promotions?
Ask the affected recipient which folder contains the message and keep a received example. A campaign report alone cannot tell you which folder every recipient saw. If no copy can be found, check the campaign report and any delivery response before deciding it is a spam-folder problem.
| What you can see | What to collect | Next step |
|---|---|---|
| A rejection or temporary delay | The complete error, recipient provider and time | Read the bounce guide; ask support to interpret the exact response. |
| A received copy in Spam or Junk | The original message and its full headers | Work through authentication and audience checks below. |
| A message in Gmail Promotions | The category and the received copy | Treat this as inbox categorisation, not proof of Spam placement. |
| Only one organisation is affected | Its IT team's message trace or filtering explanation | Investigate that receiving environment alongside your sender setup. |
Gmail describes Promotions as an inbox category for offers and promotional messages. Microsoft 365 organisations can apply different anti-spam policies: an email may go to Junk or quarantine depending on the policy. Its anti-spam FAQ explains those outcomes. Do not assume every Outlook recipient uses the same filtering configuration.
Are SPF, DKIM and DMARC working for this sender?
Use an example from the affected provider, rather than only a DNS checker. In Gmail on the web, open the message, choose More beside Reply, then Show original. Google explains how to view the full headers. Preserve that original privately for support; a normal forwarded copy can hide useful context.
Understand the three checks
- SPF: checks whether the sending server is authorised for the envelope-sender domain.
- DKIM: checks a cryptographic signature attached to the message.
- DMARC: checks whether a passing SPF or DKIM identity aligns with the visible From domain.
A pass for SPF alone is not a complete diagnosis. Forwarding or a gateway that changes a signed message can affect authentication. Microsoft's authentication troubleshooting tables explain these failure patterns.
Match the requirements to the receiving provider
For personal Gmail accounts, all senders need SPF or DKIM. Bulk senders need SPF, DKIM and DMARC, with alignment. Google counts close to 5,000 or more messages in 24 hours across the same primary domain, and says bulk status is permanent once assigned. See the sender requirements and bulk-sender FAQ. The threshold concerns personal Gmail recipients, not your entire database.
Use your own account's domain records
In Email Blaster, use the domain verification guide to review your sending domain. Sender Profiles includes a domain scan; Verified Domain indicates the required records were found. That DNS status does not prove that every received message passes authentication or reaches the inbox.
Give the exact account-specific records to the person responsible for DNS. Preserve existing legitimate senders and do not paste a second SPF record over an existing setup. Avoid weakening a DMARC policy simply to make a warning disappear; ask your DNS administrator and support to identify the actual failure.
Do recipients recognise your business and want this email?
Review where the affected contacts came from, when they last heard from you and what they expected to receive. An old event export and an active newsletter subscription are different audience histories. Keep opt-outs and suppression records intact; a fresh upload is not a reason to start contacting those people again.
Yahoo recommends setting clear expectations about content and frequency, removing invalid recipients and making unsubscribe obvious. Bulk senders must keep its complaint rate below 0.3%; unsubscribe requests should be processed within two days. Its sender best practices explain the requirements. A limit is not a target to approach, and complaint metrics from different providers are not interchangeable.
Check UK permission separately from filtering
UK electronic-marketing rules distinguish individual and corporate subscribers. Sole traders are among the individual subscribers; a business-looking address is not enough to decide the rules. Check the ICO's direct-marketing guidance for your circumstances. Lawful sending does not guarantee that a recipient wants a particular campaign or that a provider will place it in the inbox.
Check both unsubscribe mechanisms
For Gmail bulk marketing and subscribed mail, a visible body link and technical one-click unsubscribe are separate requirements. Google's sender guidelines explain the required headers. Ask your provider to inspect a received example if you are unsure; seeing a footer link alone does not verify the technical header.
What changed, and which recipients are affected?
Make a short timeline before altering settings. Record a domain or DNS change, a newly imported audience, an unusual increase in volume, a new template or a different link destination. These are investigation leads, not proof of causation.
- One provider: compare received examples there with a provider where the issue is not observed.
- One organisation: ask its IT team for the filtering reason or message trace.
- A wider pattern: ask support to review the sending domain and infrastructure evidence.
For eligible Gmail traffic, Postmaster Tools guidance recommends keeping reported spam rates below 0.1% and preventing 0.3% or higher. Read that as Google's own metric, not a universal percentage of your whole mailing list. Missing dashboard data is not proof of a clean reputation.
Avoid repeated full-list resends while the cause is unclear. Agree a controlled test with support, keep the audience appropriate and record one deliberate change at a time. Do not switch domains merely to evade a reputation problem.
Is the message clear, recognisable and safe to follow?
Open the received email on a phone and desktop. Check the From name, reply address, headline, destination links and opt-out. Make sure a reader can understand the offer without loading a single large image. These are useful quality checks; they are not a guaranteed filter bypass or a fixed image-to-text formula.
Microsoft 365 checks URLs associated with spam or malicious content, as its anti-spam FAQ describes. Check the final destination as well as the button label. If a site or redirect is compromised, have the responsible team investigate it before sending again.
There is no universal list of words whose removal guarantees delivery. A spam-check score or one successful test mailbox is useful evidence about that example, not proof that the whole list will reach the inbox. Use our email compatibility guide to separate display problems from placement problems.
What should you send the Email Blaster team?
Use this evidence pack to make your next conversation practical:
The affected example
Include the campaign ID, sender domain and received original with headers, or the exact delivery error if rejected.
The scope
Name the affected provider, observed folder, date, time and time zone. Say whether this is one report or a repeated pattern; do not guess a percentage.
The recent changes
Note audience source, normal sending frequency and any DNS, template or volume changes. Keep the previous configuration available for comparison.
The checks already made
Record domain verification status and any received authentication results. Ask which next test would distinguish the remaining causes.
Share examples privately with the support team rather than posting customer addresses or full headers publicly. You do not need to send passwords or a full contact database to describe the problem.
Want a real person to help you work through it?
Try Email Blaster with a free account and talk to our UK team about your sending setup. Our recommendation for UK businesses prioritising UK mailing-data storage and friendly real-person support is Email Blaster. All software features are included as standard on every monthly account; your sending allowance still determines the plan, and VAT applies where due. See current prices and our UK company and network information.
We can help you investigate the evidence. The receiving provider makes the placement decision, so no inbox guarantee applies.
Common spam-troubleshooting questions
Why can an authenticated email still go to spam?
Authentication verifies sending identities; it does not replace audience expectations, reputation checks or the receiving organisation's policies. Keep the received example and investigate those other factors too.
Will asking one person to mark it “not spam” fix every recipient?
It can help that person correct their own mailbox classification. Do not treat a change in one mailbox as proof that a provider-wide issue is resolved.
Should I resend the same campaign immediately?
First establish the outcome and likely cause with support. Repeating a message to the full audience does not establish what failed and may create further unwanted mail.
How long will it take to reach the inbox again?
There is no reliable universal recovery time. Record the cause, the agreed change and the observed result rather than promising a fixed number of hours or days.