Here’s a number every email marketer in Australia should have taped to their monitor: 0.3%. That’s the spam complaint rate Gmail treats as the red line for bulk senders. Cross it consistently and your emails stop landing in the inbox, no matter how good your subject lines are. Stay under 0.1% and you’re in good shape.
In 2026, deliverability isn’t a technical afterthought you hand to IT. Gmail, Yahoo and Microsoft have all moved from “recommended best practice” to hard enforcement, and non-compliant mail is now being rejected outright rather than quietly filtered. If your open rates have slid over the past year and you’ve blamed the creative, there’s a decent chance the real problem sits in your DNS records.
This is the practical checklist I run through with clients to make sure their emails actually arrive.
What the inbox providers now require
The rules started with Gmail and Yahoo’s bulk sender requirements in 2024, and Microsoft followed for Outlook.com, Hotmail and Live addresses in 2025. The thresholds differ slightly, but if you send more than around 5,000 emails a day to any of these providers, you’re treated as a bulk sender. In practice, every business should meet these standards regardless of volume.
The non-negotiables
- SPF — a DNS record listing which servers are allowed to send email for your domain.
- DKIM — a cryptographic signature proving the message wasn’t altered and genuinely came from your domain.
- DMARC — a policy that tells receiving servers what to do when SPF or DKIM fails, and sends you reports on who’s sending as your domain. A policy of p=none is the minimum; the “From” domain must align with SPF or DKIM.
- One-click unsubscribe — the List-Unsubscribe header that lets people opt out straight from the Gmail or Yahoo interface, with requests honoured within two days.
- Low spam complaints — under 0.3%, ideally under 0.1%, as measured in Google Postmaster Tools.
Most reputable email platforms (Klaviyo, Mailchimp, HubSpot, ActiveCampaign and the like) handle the unsubscribe header for you. Authentication is where businesses get caught out, because it needs to be configured on your domain, not just the platform’s.
The most common deliverability mistakes I see
1. Sending from a shared or default domain
If your newsletters go out from something like [email protected], you’re borrowing someone else’s reputation and failing DMARC alignment. Set up a branded sending domain and authenticate it properly. Many brands use a subdomain such as mail.yourbrand.com.au for marketing so any reputation issues don’t touch the main domain your team uses for day-to-day email.
2. Forgetting about “shadow” senders
Your CRM, invoicing software, booking system, helpdesk and website contact forms all send email as your domain. When you tighten your DMARC policy, any of these that aren’t in your SPF record or signing with DKIM will start failing. DMARC reports are how you find them. Read them before you move from p=none to quarantine or reject.
3. SPF records with too many lookups
SPF has a hard limit of 10 DNS lookups. Every “include” for a new tool eats into that. Go over and SPF fails for everything, which is surprisingly common in businesses that have added tools over several years without anyone owning the DNS.
4. Mailing old, unengaged lists
A list of 40,000 contacts who haven’t opened anything in 18 months isn’t an asset. It’s a liability. Low engagement tells inbox providers your mail isn’t wanted, and dormant addresses can be recycled into spam traps. Sending a “we’re back!” blast to a cold list is one of the fastest ways to tank a domain’s reputation.
5. Treating complaint rate as someone else’s problem
Complaints come from people who don’t remember signing up, get more email than they expected, or can’t find the unsubscribe link. Those are marketing decisions, not technical ones.
A practical deliverability plan for 2026
Here’s the order I’d tackle things in if you’re starting from scratch or suspect something’s off.
Week 1: Audit and authenticate
- Check your SPF, DKIM and DMARC records using a free lookup tool such as MXToolbox or your email platform’s domain checker.
- List every system that sends email on your behalf and confirm each one is authenticated.
- Publish a DMARC record at p=none with a reporting address if you don’t have one, and use a DMARC reporting service to make the XML reports readable.
- Set up Google Postmaster Tools and Microsoft SNDS so you can see your domain and IP reputation directly.
Weeks 2–4: Clean the list
- Segment subscribers by last engagement (for example 0–90 days, 91–180 days, 181+ days).
- Run a short re-engagement sequence to the 181+ day group, then suppress anyone who doesn’t respond.
- Remove hard bounces immediately and use double opt-in on new sign-ups where practical.
Month 2 onwards: Tighten and monitor
- Once DMARC reports show all legitimate sources passing, move to p=quarantine, then p=reject. This also protects your customers from people spoofing your domain.
- Check Postmaster Tools weekly. A spam rate creeping above 0.1% is your early warning.
- Consider BIMI once you’re at enforcement. It displays your logo in supporting inboxes and rewards the effort you’ve put into authentication.
Don’t forget the Australian rules
Global inbox requirements sit on top of local law, not instead of it. Under the Spam Act 2003, commercial emails sent to Australians need consent, must clearly identify the sender, and must include a functional unsubscribe that’s actioned within five business days. The ACMA actively enforces this, and it has issued significant penalties to well-known Australian brands over unsubscribe failures and sending without consent.
The good news is that everything that keeps you compliant here also helps deliverability. Clear consent means fewer complaints. Easy unsubscribes mean fewer people hitting “report spam” as a shortcut.
Deliverability is a trust score. Authentication proves who you are; engagement proves people want to hear from you. You need both.
The takeaway
If email is a meaningful revenue channel for your business, spend an hour this week on three things: confirm SPF, DKIM and DMARC are passing and aligned on your sending domain, connect Google Postmaster Tools, and check your spam complaint rate. If any of those turn up a problem, fix it before you spend another dollar on creative or list growth.
The brands winning in the inbox in 2026 aren’t necessarily sending the cleverest emails. They’re the ones whose emails actually arrive.
