In the US market, both Contabo and IONOS allow inbound port 25, which is critical for mail-receiver configurations — so there’s no functional limitation there.
The real difference lies in reliability and support reputation:
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Contabo (Trustpilot 4.2/5, ~6,700 reviews) offers aggressive pricing and high specs, but US-based users often report high latency, slower support response, and performance instability, especially under load. Contabo’s US data centers exist, but they’re not always as responsive as expected.
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IONOS (Trustpilot 4.5/5, ~31,000 reviews) performs better in the US than many assume. It has a stronger support reputation and more reliable infrastructure, with fewer 1-star reviews (~10% vs Contabo’s 16%). Users consistently report better uptime, live support, and account management compared to Contabo.
Conclusion (US):
If you’re US-based and need stability, fast support, and low risk for production workloads, IONOS is the safer pick. Contabo may still be worth considering for dev/test environments or cost-sensitive deployments, but expect trade-offs in latency and support quality.