This PR was merged into the 6.4 branch.Discussion----------[Mailer] Fix Sendmail memory leak| Q             | A| ------------- | ---| Branch?       | 6.4 <!-- see below -->| Bug fix?      | yes| New feature?  | no <!-- please update src/**/CHANGELOG.md files -->| Deprecations? |no <!-- please update UPGRADE-*.md and src/**/CHANGELOG.md files -->| Issues        |Fix#50486 <!-- prefix each issue number with "Fix #", no need to create an issue if none exists, explain below instead -->| License       | MITPrevious PR:#59239Fixes issue#50486 (Sendmail transport runs out of memory).- I have removed unrelated changes that somehow got in the previous attempt of pull request because of wrong base version.- As for the "metrics about the memory leak itself" - it is in the issue 50486. When write(), which is defined in vendor/symfony/mailer/Transport/Smtp/Stream/AbstractStream.php, is called without $debug parameter, it's true by default, and $this->debug gets appended all the email body data incrementally.  So for example if you have loop sending personalized emails to 200,000 subscribers 20 kB each, $this->debug becomes 4 GB, plus overhead, and the script runs out of resources.  The fix eliminates the problem.<!--Replace this notice by a description of your feature/bugfix.This will help reviewers and should be a good start for the documentation.Additionally (seehttps://symfony.com/releases): - Always add tests and ensure they pass. - Bug fixes must be submitted against the lowest maintained branch where they apply   (lowest branches are regularly merged to upper ones so they get the fixes too). - Features and deprecations must be submitted against the latest branch. - For new features, provide some code snippets to help understand usage. - Changelog entry should followhttps://symfony.com/doc/current/contributing/code/conventions.html#writing-a-changelog-entry - Never break backward compatibility (seehttps://symfony.com/bc).-->Commits-------c74e2a3 fix_50486 - memory leak