Email troubleshooting guide
SMTP port 25 blocked? First decide whether the problem is sending or receiving.
"Port 25 blocked" can mean two different things. If email will not leave your server, that is an outbound problem. If outside mail cannot reach your server, that is an inbound problem. The fix is different for each one.
I cannot send email
Your ISP, cloud host, or network may block outgoing SMTP on port 25. Use an authenticated relay on alternate ports so your mail server, app, printer, or device can send reliably.
Use SMTP RelayI cannot receive email
Your ISP may block incoming SMTP traffic to your server. Use Mail Redirection so DNSExit receives mail on port 25 and forwards it to your server on an alternate open port.
Use Mail RedirectionWhy port 25 gets blocked
Many residential ISPs and hosting providers restrict SMTP port 25 to reduce spam and abuse. That does not always mean email hosting is impossible, but it does mean you need the right path around the block depending on whether mail is moving out of your network or trying to come in.
How to identify your problem
- Sending fails Messages stay in queue, apps cannot deliver mail, or a provider rejects outbound SMTP connections.
- Receiving fails Outside mail never reaches your server even though your domain has MX records configured.
- Both fail Some self-hosted setups need SMTP Relay for sending and Mail Redirection for receiving.
Which DNSExit service solves which problem?
| Problem | What happens | Best fit |
|---|---|---|
| Outbound port 25 blocked | Your server, app, or device cannot send mail to the internet. | SMTP Relay |
| Inbound port 25 blocked | Other mail servers cannot deliver messages directly to your server. | Mail Redirection |
| Mail server temporarily down | You want incoming mail queued until your primary server returns. | Backup MX |
Can you still host your own mail server?
Yes, in many cases. If the issue is outbound delivery, you can keep your own mail system and send through an SMTP relay. If the issue is inbound delivery, Mail Redirection lets DNSExit receive mail for your domain and forward it to your server on alternate SMTP ports such as 26 or 940.
Choose the path that matches the symptom
If mail will not send, start with SMTP Relay. If outside mail cannot reach your server, start with Mail Redirection. If you are not sure which side is failing, use the tools and FAQ pages to narrow it down first.