Email Deliverability

Email Deliverability — keeping confirmations & reminders out of spam

If clients aren't receiving booking confirmations or reminder emails, the issue is almost never the plugin's templates — it's how the message gets sent and whether the receiving server trusts your sending domain. This page walks you through the standard fixes, in order of impact.

TL;DR — three things to do

1. Send through a real SMTP provider (not your web host's PHP mail()).
2. Add SPF, DKIM, and DMARC DNS records for your domain.
3. Use a "From" address on your own domain (not @gmail.com).

The plugin includes diagnostics for all three. Run them at Settings → Caswell Booking → Tools & Diagnostics → Email Delivery Test.

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1. Send through a real SMTP provider

WordPress's wp_mail() defaults to PHP's built-in mail() function, which goes out through your hosting server (Bluehost, GoDaddy, etc.). Shared hosting servers have a poor sender reputation; large inbox providers (Gmail, Outlook, iCloud) silently drop or spam-fold those messages.

The fix

Install WP Mail SMTP (free) and route through one of:

Provider	Free tier	Notes
Gmail / Google Workspace SMTP	Free with Workspace	Easiest if you already have a Workspace mailbox. Sends "as" your real address.
SendGrid	100/day	Strong deliverability, simple setup.
Mailgun	100/day (3-month trial) then pay-as-you-go	Good for transactional.
Postmark	Pay-as-you-go (~$1.25 per 10k)	Best transactional reputation.
Amazon SES	$0.10 per 1k	Cheapest at scale; setup is fiddly.

Any of these will do more than every other tip combined.

Verification

After connecting a provider, run Tools → Email Delivery Test. The plugin reports whether wp_mail() accepted the message — a "yes" means the provider received it, then check your inbox (and spam folder).

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2. Set up SPF, DKIM, and DMARC

Even with a great provider, mail to Gmail and Outlook gets spam-filtered without these DNS records. They prove the sending server is allowed to send mail "from" your domain.

Record	Purpose
SPF (TXT)	Lists IPs / providers allowed to send from your domain.
DKIM (TXT or CNAME)	Cryptographic signature on each message.
DMARC (TXT)	Tells receivers what to do if SPF/DKIM fail (reject / quarantine / monitor).

Setup walkthrough — SendGrid

1. Sign up at sendgrid.com and verify your account.
2. Settings → Sender Authentication → Authenticate Your Domain.
3. Pick your DNS host (GoDaddy, Cloudflare, Namecheap, etc.) and enter your domain (e.g. castherapylmt.com).
4. SendGrid generates 3 CNAME records. Add them at your DNS host:

   em1234.castherapylmt.com.       CNAME  u123.wl.sendgrid.net.
   s1._domainkey.castherapylmt.com CNAME  s1.domainkey.u123.wl.sendgrid.net.
   s2._domainkey.castherapylmt.com CNAME  s2.domainkey.u123.wl.sendgrid.net.
   

5. Wait 5–60 min for DNS propagation, click Verify in SendGrid.
6. Generate an API key at SendGrid → Settings → API Keys → "Restricted Access" → enable Mail Send → Save the key.
7. Back in WordPress: install WP Mail SMTP, choose SendGrid, paste the API key, set the From address to bookings@castherapylmt.com (or whatever).
8. Run the plugin's Email Delivery Test.

Add DMARC

After SPF + DKIM pass, add a DMARC record (also a TXT record) at your DNS host:

_dmarc.castherapylmt.com   TXT   "v=DMARC1; p=none; rua=mailto:postmaster@castherapylmt.com; pct=100"

p=none means "report-only" — start there to see what's failing without rejecting anything. After a couple of weeks of clean reports, tighten to p=quarantine or p=reject.

Setup walkthrough — Google Workspace

If you already have a Google Workspace account for castherapylmt.com:

1. WP Mail SMTP → Settings → choose Other SMTP or Gmail / Google Workspace.
2. Either:
   • Use App Password: easiest. Workspace Admin → Security → 2-Step Verification → App passwords → generate one for "Mail" → paste in WP Mail SMTP.
   • Or OAuth: more work but doesn't break if password rotates.
3. Workspace handles SPF + DKIM automatically for emails sent through their SMTP. You still need a DMARC TXT record (above).

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3. Use a From address on your own domain

The plugin's Settings → Caswell Booking → Email has a From Address field. Always set this to an address on the domain you own (e.g. bookings@castherapylmt.com).

If the From address is on a free provider (@gmail.com, @yahoo.com, @outlook.com), most receivers reject the message outright due to DMARC enforcement. The plugin's Email Delivery Test now flags this with a yellow warning.

What if my domain doesn't have email yet?

Two cheap options:

• Domain registrar email forwarding — Namecheap and Cloudflare offer free email forwarding. Create bookings@castherapylmt.com and forward to your real Gmail. You can't send from it, but the plugin doesn't need to receive — only send through SendGrid/Mailgun/Postmark, which doesn't care that your domain has no inbox.
• Google Workspace — $6/mo, full mailbox. Recommended once volume picks up.

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What the plugin does on its end

When you upgrade to v1.4.7 or later, the plugin attaches these headers to every outgoing email — automatically:

• From — uses your configured From address
• Reply-To — matches the From address so client replies route correctly
• Message-ID — uniquely identifies each message; some hosts drop emails without one
• Date — explicit RFC 2822 date (some hosts mis-format wp_mail's auto-date)
• List-Unsubscribe: <mailto:From-address?subject=Unsubscribe> — Gmail and Outlook give cleaner inbox placement to messages that expose a one-click unsubscribe path. The mailto pattern routes any "unsubscribe" click straight to the practitioner.

Reminder emails also get a small visible footer link inviting clients to reply with "stop reminders" — Gmail's spam filters reward emails with clear opt-outs.

Verification checklist

After completing the steps above, send yourself a test booking and check the email's headers. In Gmail, click the message → ⋮ → "Show original". Look for:

• SPF: PASS ✓
• DKIM: PASS ✓
• DMARC: PASS ✓
• Authentication-Results: header showing all three

If any are missing or fail, that's the next thing to fix. SendGrid, Mailgun, and Postmark all have great support for diagnosing this.

Common gotchas

• Different domain in From and SMTP — sending via gmail.com SMTP but with From: name@castherapylmt.com will fail DMARC. Either send via Workspace (which signs for castherapylmt.com), or set From to the Gmail address.
• DNS not propagated — TTL can be 24 hours on some registrars. Be patient.
• Subject line too "promotional" — confirmations are transactional and rarely flagged, but reminders sometimes are. Avoid all-caps, "Free!", excessive punctuation.
• No plain-text alternative — HTML-only emails score worse on some filters. The plugin currently sends HTML only; planned for a future release.
• Sending too many at once — if you suddenly send 1000 cold-list reminders, expect a deliverability hit. The plugin's per-booking trigger keeps you well below that threshold organically.

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💡 If you're stuck after working through this page, the debug log (Tools → Debug Logging → enable, then trigger a send) shows the exact headers and the wp_mail response. Paste those into your provider's support chat — SendGrid/Mailgun/Postmark all have good first-line support for deliverability questions.