Start Postkasten
Open the Mac app and make sure the local SMTP catcher is running.
Postkasten support
Help for local email testing on macOS.
Setup notes, common fixes and support contact details for Postkasten 1.0.
Quick setup
Point your app at Postkasten.
Use local SMTP
Configure your development app to send SMTP to 127.0.0.1 on port 1025.
Send a test email
Trigger a password reset, account confirmation, invoice or other transactional email from your local app.
SMTP host: 127.0.0.1
SMTP port: 1025
Authentication: none
Encryption: noneTroubleshooting
Common fixes.
Most local email issues come from the sending app still using a real SMTP provider, a wrong port or another mail catcher already using the same port.
No emails arrive
Check that Postkasten is open, your app uses 127.0.0.1:1025, and your development server has picked up the latest mail settings.
Port 1025 is busy
Quit other local mail catchers such as Mailpit or MailHog, then restart Postkasten.
The preview differs from Gmail or Outlook
Postkasten gives local previews and compatibility hints. It does not provide real external client screenshots.
Attachments look unexpected
Treat attachments from test emails like untrusted files. Save or open them deliberately.
Purchases
App Store billing and refunds.
Postkasten is sold through the Mac App Store. Purchase history, billing and refunds are handled by Apple.
Refunds
Use Apple's App Store purchase support flow for refund requests.
Updates
App updates are delivered through the Mac App Store.
Offline use
The local email testing workflow works without a Postkasten account or cloud sync.
Contact
Still stuck?
Email support with your macOS version, Postkasten version and the framework you are sending from.
Email support
Do not send private production email content unless support explicitly asks for a sanitized example.