Check if port 587 is open
On the server, see what is listening:
sudo ss -tulpn | grep ':587 'From another machine, test reachability:
nc -zv your-server.example.com 587Port 587 (TCP) — SMTP submission
Mail submission with STARTTLS.
🔒 Runs locally — your input never leaves this browser tab
- Port
587- Protocol
- TCP
- Service
- SMTP submission
- Internet exposure risk
- Low
The recommended port for apps sending email through a provider.