hMailServer 6.2.4

A Control-Panel-focused release that completes the last functional-parity item from
the classic Administrator. The whole product is now stamped 6.2.4 — the server,
the Control Panel (window header and About page) and the installer all report the
same version, matching this release.
Active Directory account pickers (Control Panel)

The Control Panel gained a read-only Active Directory browser.

    Services/ActiveDirectoryService.cs — enumerates every domain in the current
    forest (RootDSE defaultNamingContext + the Partitions container's domain
    crossRefs, so there is no dependency on System.DirectoryServices.ActiveDirectory)
    and searches a domain's users with a single LDAP-escaped DirectorySearcher
    matching sAMAccountName / displayName / mail / userPrincipalName. Built on
    System.DirectoryServices, which net8.0-windows resolves from the Windows
    Desktop shared framework the installer already bundles. On a non-domain-joined
    machine it reports a friendly reason instead of throwing.
    Account → Directory tab — "Browse Active Directory…" opens a domain +
    search browser; the picked account fills ADDomain / ADUsername and ticks
    linked to Active Directory.
    Distribution-list recipients — "Add from AD…" multi-selects AD accounts and
    imports their e-mail addresses into the list.

Validated end-to-end against a live domain controller (progressiverobot.local):
domain enumeration, the all-users query, and the name / e-mail filters all returned
the expected results.
Other Control Panel improvements

    Clearer "settings could not be read" diagnostics. When the server returns the
    generic TargetInvocationException, the Control Panel now unwraps it and explains
    the real cause — connect with the server-administrator account, or the server
    cannot reach its database — instead of showing "Exception has been thrown by the
    target of invocation". (This is what produced the misleading "26 settings could not
    be read" message on the Protocols page for a non-admin connection.)
    About page filled out with maintainer / company details — Christopher Holloway
    / Progressive Robot Ltd (www.progressiverobot.com).

Packaging & consistency

    The vendored MariaDB Connector/C client (libmysql.dll + auth plugins) is staged
    into the build output by the server post-build step, so MySQL/MariaDB back ends
    work out of the box.
    Version consistency: server Version.h, the Control Panel assembly and the
    installer are all 6.2.4.

The Control Panel requires the .NET 8 Desktop Runtime (bundled by the installer and
installed silently when missing). For the full 6.2.x feature set — authentication
modernization (SCRAM/channel binding/Argon2id/OAuth2), Sieve + ManageSieve,
observability and deliverability — see the README and the 6.2.3 release notes.