Questions
What's the difference between port 25, 465 and 587?
Port 25 carries mail between servers. Port 587 is for apps and people sending mail, and upgrades to encryption with STARTTLS. Port 465 is also for sending, but encrypted from the start. 2525 is a non-standard alternative some providers support.
A port shows "No answer". Is the server down?
Not necessarily. "No answer" means a firewall dropped the connection, which is common for port 25 on cloud servers and home internet. "Closed" means the server is reachable but nothing listens on that port.
Does this check my own computer's ports?
No. The check runs from our server on the internet, so it shows what the outside world sees, not whether your own network blocks outgoing mail.
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