This article is about IMAP connections that never establish properly — the connection is refused, times out, or connects but never returns an IMAP greeting/banner. If instead you're getting an explicit "authentication failed" or 535 error after connecting, see I get an authentication error (535 / IMAP) when connecting my mailbox instead — that's a credentials issue, not a connectivity one.
What this usually means
A refused connection, a hang, or a connection with no banner almost always points to something on the specific backend mail server hosting your mailbox, not your email client, your credentials, or your network. Different mailboxes and domains can be routed to different servers, so this can affect only some of your mailboxes while others work fine.
Before contacting support, quickly check
You're using the exact host and port shown on your mailbox's credentials page (not a guessed or cached hostname) — see How can I access mailbox credentials in Maildoso?
The same failure happens from a different network or device — this rules out a local firewall or ISP blocking port 993
Whether it affects one mailbox, one domain, or all of them — this helps narrow down whether it's isolated to one server
What to send support
The exact IMAP host and port you're connecting to
What actually happens: connection refused, times out, or connects with no banner/greeting
The affected mailbox(es) or domain(s), and whether other mailboxes on the same account work fine
This lets us check the health of that specific server directly rather than general account troubleshooting.