Free tools
SMTP port checker
Enter hostname to test. Results reflect your current network — not MailFleet infrastructure.
What this checks
TCP reachability on ports 25, 465, and 587 with basic banner capture where permitted.
Why it matters
Firewall or ISP blocks on SMTP ports prevent sending. Confirm connectivity before configuring MailFleet.
Results
Common issues
- Testing only port 587 when the provider requires 465 with implicit TLS.
- Corporate firewalls blocking outbound SMTP from desktop networks.
- Assuming port open means authentication and relay are correctly configured.
How to fix
- Confirm provider documentation for the correct submission port and encryption mode.
- Test from the same network MailFleet will use on the desktop.
- Follow with full SMTP diagnostics including AUTH when credentials are available.
How MailFleet helps
MailFleet stores working SMTP port and encryption settings per provider profile after successful connectivity tests.
Related free tools
Delivery note: MailFleet helps users manage campaigns through their own sending providers. Delivery outcomes depend on sender reputation, DNS authentication, content quality, recipient engagement, list quality, provider rules, and mailbox filtering systems.
For regulatory context on commercial email in the United States, see the FTC CAN-SPAM compliance guide.
Frequently asked questions
Residential and some cloud networks block outbound 25 to reduce spam bot abuse. Use 587 or 465 for submission.
Get started
Prepare and control campaigns with MailFleet
Run integrated diagnostics, manage providers, and monitor campaigns from a professional desktop app.
Available on
- Windows 10+
- macOS 12+
- Linux (DEB & RPM)
Same desktop experience across every platform — one workflow for your entire team.