Forced From is lost for an unmapped sender after a mapped-address send in the same request (provider handler is a shared singleton)

[proskurius]

Version: FluentSMTP 2.3.1, WordPress 6.9.7, PHP 8.5, provider Amazon SES (any provider with force_from_email = yes should behave the same).

Setup: one SES connection, sender inform@example.org, "Force From Email" on, set as default; mappings only for inform@ and a fallback connection. Site code and WooCommerce send some mail with From: contact@example.org (unmapped).

Expected: every unmapped From is rewritten to the default connection's sender, as it is for a single send.

Actual: within one request, after a send from the mapped address, later sends from the unmapped address go out with their own From (contact@). Observed on a WooCommerce order: customer mail (forced OK) → site "Welcome" mail from inform@ → admin "New order" mail delivered with From: contact@.

Repro (WP-CLI, one request):

wp_mail('me@example.org', 'A', 'a', ['From: X <contact@example.org>']); // forced → inform@
wp_mail('me@example.org', 'B', 'b', ['From: X <inform@example.org>']);  // mapped
wp_mail('me@example.org', 'C', 'c', ['From: X <contact@example.org>']); // NOT forced → contact@

With an SES IAM key restricted to ses:FromAddress = inform@…, C fails with AccessDenied; with an unrestricted key it is delivered from contact@.

Cause: app/Bindings.php registers every provider handler as a container singleton. fluentMailGetProvider() (app/Functions/helpers.php) caches a driver per From address, but the per-address entries point to the same object; force_from_email_id is added only in the default-connection branch. The mapped send calls setSettings() on the shared object without that key, so the cached entry for the unmapped address no longer carries it, and FluentPHPMailer::send() skips the rewrite. The log still shows the connection's sender (BaseHandler::setFrom() reads sender_email from settings), so the leak is invisible in the FluentSMTP log.

Suggested fix: resolve a fresh handler per lookup ($app->make() without the singleton binding), or re-apply the per-address settings (including force_from_email_id) on every fluentMailGetProvider() hit instead of trusting the cached object.