A reminder email that lands in the spam folder is the same as no reminder at all. Email deliverability is the difference between a 95% read rate and a 30% read rate.
The good news: deliverability is mostly a technical setup, not ongoing work.
The three records every business needs
Three DNS records — once configured, they stay configured.
1. SPF (Sender Policy Framework)
A TXT record on your domain that lists which servers are allowed to send email “from” your domain.
Example for a domain using SendGrid + Google Workspace:
v=spf1 include:sendgrid.net include:_spf.google.com ~all
Without SPF, mail providers treat your emails as suspicious. Most reminders end up in spam.
2. DKIM (DomainKeys Identified Mail)
A cryptographic signature that proves the email came from your domain. Set up via your email provider (SendGrid, Postmark, Resend all auto-generate the records).
3. DMARC (Domain-based Message Authentication)
A policy record that tells mail providers what to do if SPF or DKIM fail. Start with:
v=DMARC1; p=none; rua=mailto:[email protected]
p=none is “monitor only” — gives you reports without
blocking anything yet. After 30-60 days, if reports look
clean, escalate to p=quarantine then p=reject.
Sender reputation
Mail providers track each sending domain’s reputation:
- Are emails being marked as spam by recipients?
- Are emails bouncing because addresses don’t exist?
- Are emails being opened?
A new domain with no reputation history starts neutral. Your first 1,000 emails establish the reputation.
To build good reputation:
- Send only to people who explicitly opted in (booked an appointment counts)
- Remove bouncing addresses immediately
- Don’t blast a stale list
What triggers spam filters
Common content patterns that hurt deliverability:
Subject line red flags:
- ALL CAPS
- Excessive exclamation marks (!!!)
- Currency symbols ($$$)
- Words like “FREE”, “GUARANTEE”, “URGENT”
Body content red flags:
- Image-only emails (no plain text)
- Excessive links (more than ~5)
- Marketing copy in transactional emails
- Spelling errors
Technical red flags:
- Sending from a generic Gmail/Yahoo address (
[email protected]) — looks unprofessional and triggers filters - HTML without plain-text alternative
- Suspicious sender name vs sender email mismatch
Why BYO email matters here
If your booking platform sends reminders from
[email protected], the customer sees an email
from a domain they don’t recognise. Spam filters treat it
suspiciously, and customers ignore it.
If reminders come from [email protected], the
customer recognises the sender, the domain has positive
reputation built up over time, and inbox placement is
better.
This is one of the best arguments for bring-your-own email provider (which Zedule supports natively).
Provider-specific tips
Gmail (the largest provider):
- Aggressive spam filtering — needs SPF/DKIM/DMARC
- Promotional tab is fine for marketing but BAD for reminders — customers don’t check the Promo tab
- Plain text + minimal HTML works best
Outlook:
- Picky about display names; use “Looks Salon” not “looks_salon_bookings”
- Penalises high image-to-text ratio
Apple Mail:
- Generally relaxed
- Renders custom fonts correctly (rare)
How to test deliverability
Run your reminder through a tool like mail-tester.com before launching. The tool gives a 0-10 score.
Aim for 9+/10. Below 7/10 means your reminders will land in spam at scale.
Spam complaint rate
Mail providers track what percentage of recipients mark your email as spam. Above 0.1% (1 in 1000) is the threshold for trouble.
For appointment reminders, complaint rates are usually near zero — customers expect the email and don’t mark it as spam.
If your complaint rate climbs, the cause is usually:
- Sending to old addresses that don’t recognise your business
- Sending too far in advance (customer forgot they booked)
When deliverability falls
Symptoms:
- Customers say “I never got the reminder”
- Open rates drop suddenly
- Email provider shows bounces climbing
Diagnosis:
- Check SPF/DKIM/DMARC records still exist
- Check sender reputation at postmaster.google.com
- Test deliverability with mail-tester
- Check your email provider’s bounce/complaint dashboard