CAMEL-23522: doc-sync 4.14 upgrade guide for camel-mail mail.smtp.* gating

[oscerd]

Summary

Doc-sync of the camel-mail mail.smtp.* gating entry from camel-4.14.x onto main's copy of camel-4x-upgrade-guide-4_14.adoc, per the project's backport upgrade-guide policy in CLAUDE.md:

The camel-4x-upgrade-guide-4_XX.adoc files for ALL versions live on main and act as the canonical history across all releases. When a PR is backported to a maintenance branch and adds an upgrade-guide note for that release line, the corresponding entry must ALSO be added to the matching camel-4x-upgrade-guide-4_XX.adoc file on main.

This PR mirrors the entry added in #23416 (backport to camel-4.14.x) onto main, immediately after the existing camel-elasticsearch-rest-client entry in the "Upgrading from 4.14.3 to 4.14.8" section.

Linked

• Main PR: CAMEL-23522: camel-mail - gate JavaMail session properties from headers behind opt-in #23362 — CAMEL-23522: camel-mail - gate JavaMail session properties from headers behind opt-in (merged)
• 4.18.x backport: [backport camel-4.18.x] CAMEL-23522: camel-mail - gate JavaMail session properties from headers behind opt-in #23381 (open)
• 4.18 doc-sync on main: CAMEL-23522: doc-sync 4.18 upgrade guide for camel-mail mail.smtp.* gating #23383 (open)
• 4.14.x backport: [backport camel-4.14.x] CAMEL-23522: camel-mail - gate JavaMail session properties from headers behind opt-in #23416 (open)
• Jira: https://issues.apache.org/jira/browse/CAMEL-23522
• Family precedent: CAMEL-23222 / CVE-2025-27636

Notes on the 4.14 wording

The 4.14.x branch only extracts mail.smtp.* (not mail.smtps.*) on the producer side — the mail.smtps. fallback was introduced later by CAMEL-22900. The entry therefore references only mail.smtp.* for the producer-side gating. The MailHeaderFilterStrategy inbound filter on 4.14.x does block both prefixes as forward-looking defense in depth, which is reflected in the last paragraph.

Test plan

• Single docs file added; no code changes.
• Wording matches the same section on the camel-4.14.x branch.

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Claude Code on behalf of Andrea Cosentino

[github-actions]

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[github-actions]

🧪 CI tested the following changed modules:

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[gnodet]

Content is accurate, correctly placed (in the "Upgrading from 4.14.3 to 4.14.8" section after camel-elasticsearch-rest-client), and follows the same pattern as the already-merged 4.18 doc-sync (#23383). CI is green.

Claude Code on behalf of Guillaume Nodet