senn-techNoSpamProxy vs. Proxmox Mail Gateway: two routes to a clean inbox
The question comes up in every other mail project: NoSpamProxy or Proxmox Mail Gateway? Both sit at the same point in the mail flow, both filter spam and malware, both have satisfied users.
We have written about each separately — on NoSpamProxy and on the Proxmox Mail Gateway. This is the head-to-head, and the honest answer is: they do not differ where most people look.
The same place in the mail flow
Both are a gateway, not a mail server. They accept the message before your actual mail server sees it — which keeps that server unreachable from outside.
The filtering foundations are similar too: sender reputation, SPF, DKIM, DMARC, greylisting, content analysis. Anyone shopping for the better hit rate is comparing the wrong property — both deliver when configured well.
Where NoSpamProxy genuinely leads
Encryption is core, not an add-on. S/MIME and PGP including certificate management are built in, as is sending large files to recipients whose mailbox will not take the attachment. In an open-source chain you would assemble and maintain those pieces yourself.
Analysis rather than raw data. Around DMARC the vendor offers reporting that turns aggregate reports into actionable recommendations, plus a service for early malware detection. The current server release, 16.2, is built on .NET 10 and adds more precise MIME-type detection and OpenTelemetry support for monitoring. Anyone who has tried to read DMARC XML by hand knows what that processing is worth.
A vendor with a phone number. Net at Work is based in Germany, there is a support contract and a roadmap. For companies without in-house mail expertise that is not a footnote — it is often the actual reason.
Where Proxmox Mail Gateway genuinely leads
Extensibility. PMG is open source and accepts your own inspection stages. You can hang real filters into the mail flow — actual code, not just rules in a GUI. That is simply not possible with a closed product.
Cost model. No per-mailbox licence; the support subscription is optional. As user numbers grow, that behaves fundamentally differently from per-seat licensing.
Platform. Debian rather than Windows. Whether that is an advantage depends on the house — in an already Linux-shaped environment it is one, in a pure Windows estate it is a foreign body.
What this means in our own operations
We run the Proxmox Mail Gateway as our MX front end — and in exactly the configuration that makes the difference: alongside the standard checks, our own inspection stages sit in the mail flow, among them an AI-assisted classification and a check on links in inbound mail.
That is the honest core of this comparison. We did not choose PMG because it filters better — we chose it because we wanted to build things into the mail flow that cannot be bought ready-made. Without that need, PMG gives away precisely the advantage you are paying for with operational responsibility.
And it does cost. A gateway is not an appliance you install and forget: quarantine needs reviewing, misclassifications need correcting, blocklist entries need watching. That work exists with both products — with a commercial one, the vendor carries only part of it.
The question that actually decides
Not "which filters better", but:
Do you want to be able to intervene in the mail flow — or do you want somebody else to be accountable for it?
Both are legitimate answers. Answer it honestly and the product choice is already made. For companies with high encryption requirements, a Windows estate and no mail team, NoSpamProxy is the shorter path. For companies that treat the mail flow as a process of their own and want to extend it, it is the Proxmox Mail Gateway.
Conclusion
Two good products, two different philosophies — and a comparison that fails on hit rate because both deliver there. What decides is encryption, extensibility, and who shoulders operations.
One piece of advice regardless of the choice: work out first who looks at the quarantine each morning. If that question has no answer, that is the real problem — and no product solves it.
Further Reading
Which of the two filters better?+
That question misleads. Both reach very good detection rates when configured properly, and both rest on the same foundations: sender reputation, SPF, DKIM and DMARC, greylisting and content analysis. The difference is not the hit rate but encryption, extensibility, platform and operating model. Looking for the better filter means comparing the wrong property.
When is NoSpamProxy the right choice?+
When encryption is a core requirement rather than a side topic. NoSpamProxy ships S/MIME and PGP with certificate management, plus large file transfer, as part of the product — with an open-source chain you would assemble those pieces yourself. Add a German vendor with a support contract and a homogeneous environment for companies already running on Windows.
When is Proxmox Mail Gateway the right choice?+
When you want to keep the filtering logic in your own hands. PMG is open source, runs on Debian and can be extended with your own inspection stages — your own milters, rules and integrations. It carries no per-mailbox licence cost, with an optional support subscription. The price is operational responsibility: you need somebody who understands and maintains it.