Sound familiar?
- Campaigns that used to get clicks are now getting almost none.
- Gmail shows a spam rate warning in Postmaster Tools, or you have never set Postmaster Tools up.
- Outlook and Hotmail addresses are bouncing with authentication errors.
- Your list includes old, bought or scraped addresses and bounce rates are climbing.
- You send to your whole list every time, regardless of engagement.
- Your unsubscribe link goes to a login page or takes days to work.
Key facts
- Deliverability reviews and fixes are charged at £45 an hour + VAT, with a fixed quote agreed first.
- Google's sender guidelines apply bulk rules to senders of more than 5,000 messages a day to Gmail accounts.
- Gmail bulk senders need SPF, DKIM and DMARC (p=none is the minimum), plus one-click unsubscribe on marketing mail.
- Google asks senders to keep the Postmaster Tools spam rate below 0.1% and never reach 0.3%.
- Yahoo's Sender Hub asks senders to honour unsubscribes within 2 days.
- Microsoft began enforcing similar rules for Outlook.com, Hotmail and Live addresses on 5 May 2025.
The bulk sender rules, in one place
Since 2024 the big mailbox providers have set out clear minimum standards. Here is what their own documentation says, checked in October 2026:
| Provider | Who it applies to | Key requirements |
|---|---|---|
| Gmail (Google Email sender guidelines) | Senders of more than 5,000 messages a day to Gmail accounts | SPF, DKIM and DMARC (p=none allowed), From domain aligned with SPF or DKIM, one-click unsubscribe on marketing mail, TLS, valid PTR records, spam rate below 0.3% |
| Yahoo (Sender Hub best practices) | Bulk senders | SPF and DKIM, DMARC at p=none or stronger that passes, one-click unsubscribe, honour unsubscribes within 2 days, spam rate below 0.3% |
| Microsoft Outlook | Domains sending more than 5,000 emails a day to Outlook.com, Hotmail and Live | SPF and DKIM pass, DMARC at p=none or stronger aligned with the From domain, enforced from 5 May 2025 |
dmarcian reported that Microsoft moved to rejecting non-compliant mail outright rather than sending it to Junk. Even if you send fewer than 5,000 a day, these rules describe what inbox providers expect from anyone sending marketing.
Authentication is the floor, not the ceiling
SPF, DKIM and DMARC prove that mail claiming to be from your domain really is. They are essential, but passing them does not guarantee the inbox. Once a provider knows who you are, it judges whether people want your mail. That is reputation, and it is built from complaints, engagement, bounces and consistency.
The DNS side of authentication, including fixing SPF records, rotating DKIM keys and moving DMARC from p=none to quarantine or reject, is covered in depth by our sister company's email deliverability support service. On this page we focus on the marketing side: what you send, who you send it to and how often.
Complaints, the number that matters most
Google's guidelines tell senders to keep the spam rate reported in Postmaster Tools below 0.1% and to avoid ever reaching 0.3%. That is one complaint per thousand recipients as a target. Yahoo calculates its rate only from mail delivered to the inbox, so it can look higher than your own figures suggest.
Complaints usually come from the same few causes:
- People who do not remember signing up, often from old lists or competitions
- A sudden jump in frequency, such as daily emails during a sale
- An unsubscribe link that is hard to find, so the spam button is easier
- Content that does not match what people signed up for
We find which of these applies, then fix the cause rather than just the symptom.
List hygiene and engagement-based sending
Sending to people who never open or click tells inbox providers your mail is unwanted. We set up engagement tiers in your platform, for example engaged in the last 30, 90 and 180 days, and send most campaigns to the engaged tiers. Less engaged contacts get fewer emails and a re-engagement sequence, then are suppressed if they stay silent.
Hard bounces should be suppressed automatically after one attempt, and role addresses such as info@ or sales@ watched closely. We never recommend buying lists or appending addresses: under the ICO's PECR guidance they rarely carry valid consent for individuals, and they are a common source of spam traps.
Recovering from a reputation drop
If Gmail or Outlook has started filtering you, the fix is gradual. We pause sends to unengaged contacts, send only to your most engaged segment for a period, keep volume steady and increase it slowly as Postmaster Tools improves. One-click unsubscribe is checked using the RFC 8058 List-Unsubscribe-Post header that Google and Yahoo ask for, and visible unsubscribe links are made obvious.
Deliverability work is charged at £45 an hour + VAT with a fixed quote first. If you want ongoing help so it does not slip again, our email marketing service from £95 a month + VAT includes monthly monitoring of complaints and bounces.
What you get
- A check of your sending domain against Gmail, Yahoo and Microsoft bulk sender requirements
- Postmaster Tools and Microsoft SNDS set-up and a reading of the data
- One-click unsubscribe (RFC 8058 List-Unsubscribe header) confirmed on marketing mail
- Engagement segments and a sunset policy for inactive contacts
- Bounce and complaint handling reviewed in your email platform
- A warm-up or recovery sending plan where reputation has dropped
- A written summary of findings and fixes in plain English
How it works and what it costs
Google Ads management from £150 a month, social media management from £125 a month and email marketing from £95 a month, all + VAT. Ad spend is separate and paid to the platform. No long contracts.
Free review
We look at your current ads, social, email and analytics, or your plans if you are starting out, and tell you plainly what we would change.
Plan and price
You get a written plan with targets, budgets and a fixed monthly fee before anything starts.
Set up properly
Tracking and consent first, then campaigns, audiences, content calendars or email flows, all in accounts you own.
Run and improve
We manage it every week: search terms, bids, creative, posts and tests, cutting what does not pay and doing more of what does.
Report in plain English
A monthly report on leads, sales and cost per result, not vanity numbers, with what we will do next.
Frequently asked questions
Do the Gmail bulk sender rules apply to small businesses?
The strict bulk rules apply above 5,000 messages a day to Gmail accounts. All senders still need SPF or DKIM, TLS and a spam rate under 0.3% according to Google's sender guidelines. In practice, meeting the bulk standard is the safest approach whatever your size.
What spam complaint rate is acceptable?
Google asks senders to stay below 0.1% in Postmaster Tools and never reach 0.3%. Yahoo uses the same 0.3% ceiling. Above that, you can expect more mail to be filtered or rejected.
What is one-click unsubscribe?
It is a List-Unsubscribe header defined in RFC 8058 that lets Gmail and Yahoo show an unsubscribe button next to your sender name. Recipients leave in one click without visiting a page. Most major email platforms add it automatically when set up correctly.
How quickly must we process unsubscribes?
Yahoo's Sender Hub asks bulk senders to honour unsubscribes within 2 days. Most email platforms do it instantly, but if you sync lists from a CRM, a delayed sync can break this rule.
Is DMARC p=none enough?
It meets the minimum for Gmail, Yahoo and Microsoft. It only monitors though, so it does not stop someone spoofing your domain. Moving to quarantine or reject once all your senders pass is better protection.
How much does a deliverability review cost?
dijitul marketing charges £45 an hour + VAT and agrees a fixed quote before starting. A typical review covers domain authentication, Postmaster Tools data, list hygiene, complaint sources and a written plan.
How long does it take to recover inbox placement?
It varies with how far reputation has fallen and how much you send. Recovery usually means several weeks of steady sending to engaged contacts only. We will not promise a date, but we report progress from Postmaster Tools each week.
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