Sending email from a Contabo VPS: request port 25, or relay on 587
Contabo VPS and dedicated servers have outbound port 25 disabled until you request it in the customer control panel; IP reputation is poor on many blocklists. How to relay on 587 with an authenticated SMTP provider instead.
Contabo outgoing mail server: none from Contabo — relay through smtp.queensmtp.com on 587/465.
Contabo SMTP settings at a glance
| Outgoing (SMTP) host | none from Contabo — relay through smtp.queensmtp.com on 587/465 |
|---|---|
| Ports & encryption |
587 — STARTTLS465 — SSL/TLS25 — — <em>(disabled by default; enable via the control panel with justification)</em> |
| Username | your relay SMTP username |
| Password | your relay SMTP password |
| Authentication | Contabo enables port 25 on request; most Contabo IP ranges are listed on UCEPROTECT and sometimes Spamhaus, so direct delivery to Gmail/Outlook is unreliable even when open. |
How to set up Contabo SMTP
- Relay via smtp.queensmtp.com:587 from the application or via Postfix relayhost.
- If you insist on direct delivery: request port 25, set rDNS, publish SPF/DKIM/DMARC — and expect blocklist issues.
Sending limits
- No mail service from Contabo.
Things that catch people out
- Cheap VPS ranges are the most blocklisted IP space on the internet; the relay's reputation is what gets you into the inbox.
Common Contabo SMTP errors
| Server reply | Meaning | Fix |
|---|---|---|
554 5.7.1 Service unavailable; Client host blocked using zen.spamhaus.org | Your VPS IP is listed. | Send via a relay with clean IPs. |
More codes: 535 authentication failed, 550 relay denied, 554 rejected as spam, connection timed out — or all SMTP error codes.
When Contabo is not enough for your app
When a provider caps you or blocks a port, point the same app at QueenSMTP instead: host smtp.queensmtp.com, port 587 (STARTTLS) or 465 (SSL), your SMTP username and password from the dashboard. $5/year plus $0.10 per 1,000 emails, 100 free a day to test.
Get SMTP credentials — free to test Test your relay nowRelated settings
Contabo SMTP — questions
Through an authenticated relay on 587, yes. Direct port-25 delivery requires enabling the port in the panel and still suffers from the IP range's reputation.
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