What Email Features Does Cloudron's Built-in Mail Server Offer?

Cloudron's built-in mail server is a full mail stack that runs on your own server, not just a forwarding layer. According to Cloudron's own description, it is a "modern solution with calendar, contacts sharing and self-training spam filter," and it handles the DNS authentication records (DKIM, SPF, DMARC) automatically so that mail you send is accepted by major providers. It is worth considering if you want mail, calendars, and contacts to live alongside your self-hosted apps under one user management system — and less suitable if you only need outbound transactional email or want to keep mail on a separate provider.

Core mail server capabilities

Cloudron describes the mail server as feature-packed, with these documented capabilities:

• Catch-all addresses — accept mail sent to any address at a domain, not only defined mailboxes.
• Subaddresses and tags — plus-addressing style variants so users can sort or filter incoming mail.
• Per-domain mail relays — route outgoing mail for a specific domain through a chosen relay.
• Cross-domain email aliases — an alias on one domain can point to a mailbox on another.
• Delivery logs — visibility into what happened to messages.
• Custom spam filtering rules — beyond the default self-training filter, you can define your own rules.

Automated DNS setup for deliverability

The page states that DKIM, SPF, and DMARC setup is "completely automated" for reliable mail delivery. In practice this means Cloudron generates the required DNS records for your domain and you publish them at your DNS provider. This is the part most self-hosted mail setups get wrong, and it is the main reason Cloudron frames its mail server as a "modern solution" rather than a raw MTA.

Calendar and contacts sharing

Calendar and contacts sharing is listed as part of the mail server feature set, so users on the same Cloudron instance can share calendars and address books rather than each running an isolated client-side store.

How it fits with the rest of Cloudron

The mail server is not a separate product you bolt on. It sits under the same central user management described on the page: you invite users, configure which apps they can access, and they use the dashboard to open their apps. Mail, calendar, and contacts are part of that same account model.

Two related properties from the page matter for mail specifically:

• Backups — encrypted backups can be stored on external storage such as Amazon S3, Google Cloud Storage, and Digital Ocean Spaces, which covers mail data as part of the server.
• Portability — Cloudron's immutable infrastructure design is described as allowing you to move your entire server, with all its apps, to another cloud provider. That matters for mail because moving a mail server normally means re-issuing DNS and risking deliverability.

What to check before committing

• DNS control — automated DKIM/SPF/DMARC setup still requires you to be able to publish records for the domain. If you do not control DNS, this will not work.
• Relay requirements — some hosting providers block outbound port 25. The per-domain mail relay feature is the documented way to route around that, but confirm your provider's policy first.
• Pricing and plan limits — the page links to a Pricing page but does not state prices or which mail features are gated behind which plan. Check the Pricing page directly rather than assuming the mail server is included at every tier.
• Demo access — the page offers a demo with username cloudron and password cloudron, which is the fastest way to inspect the mail, calendar, and contacts interfaces before installing.

If your goal is a single self-hosted system where mail, calendars, contacts, and apps share one user directory and one backup path, Cloudron's mail server covers that. If you need only SMTP relay for app notifications, or you want mail hosted by a third party, the built-in server is more than you need.