What the message looks like
connect to mail.example.com[192.0.2.1]:25: Connection timed outconnect to mail.example.com[192.0.2.1]:25: No route to hostlost connection with mail.example.com[192.0.2.1] while receiving the initial server greeting
What it means
The sending server found the recipient's mail server in DNS but couldn't connect to it, or lost the connection before it got going. The standard name for this status is "no answer from host".
It's temporary, so the sending server keeps the email and retries. Most servers keep trying for several days before giving up and sending a bounce, often with wording like "delivery time expired" or "message expired".
Common causes
- The receiving mail server is down or overloaded.
- A firewall is blocking connections on port 25.
- The domain's MX record points to a server that no longer exists or no longer runs email.
- A network problem somewhere between the two servers.
If you're the recipient
If it's your own domain, check your mail server is running and reachable, and that your MX records point to the right place. If you use a big email provider, it's usually a short outage, and the email arrives once it's back.
If you're the sender
Let your server keep retrying. If it never gets through, the recipient's mail server is probably misconfigured or gone, and you'll need to reach them another way.
If you use addy.io
addy.io retries forwarded emails automatically, so they're usually just delayed. If your recipient's mail server stays unreachable, the email ends up on your Failed Deliveries page. See Why are forwarded emails delayed?