VPS provider notes — Docs — the lean cPanel alternative

Nimbopanel runs on any x86_64 Linux VPS. A few things are set by your provider, not by the installer, so check these once when you set up a new server.

1. Open the cloud firewall

The installer opens the ports it needs on the server's own firewall, but most providers also have a separate cloud firewall (a control-panel setting) that you must open yourself. Allow inbound:

Port	For
80, 443	Panel + websites + automatic HTTPS
25, 465, 587, 993, 143	Email (receive + submission + IMAP)
53 (TCP + UDP)	Authoritative DNS
22	SSH

2. Outbound port 25

Most budget providers block outbound port 25 to prevent spam. This blocks your customers from sending mail directly. You can't lift it from the server — it's on the provider's network. Two options: ask the provider to unblock it, or (recommended) use a relay on port 587. See Email deliverability & sending.

3. Reverse DNS (rDNS / PTR)

For the best email deliverability when sending directly (port 25 unblocked), set the server's reverse DNS to your mail hostname (e.g. mail.yourdomain.com) in the provider's control panel. A generic default PTR like vmi123456.provider.net makes receivers distrust your mail. (When you send through a relay, the relay's rDNS is used instead, so this matters less.)

Provider quick-reference

Contabo — historically listed as blocking outbound port 25, but measured on a Contabo server in August 2026 it was not: Gmail, SendGrid and two real MX hosts all answered on port 25. Check yours rather than assuming — the panel's Outgoing mail card tells you which it is. Default rDNS is generic (set a custom PTR if you send directly). Good value; the trade-offs are normal for the price.
DigitalOcean / Vultr / Linode / Hetzner — outbound 25 is typically blocked until you request it; open the cloud firewall for the ports above.
AWS EC2 — port 25 is throttled/blocked by default (request removal via the SES/limits process); Security Groups control inbound.

The pattern is the same everywhere: open the cloud firewall, and plan for port 25 being blocked outbound (relay). Everything else the installer handles.