Optimized MailManager::createSmtpTransport (#694)

• Update MailManager.php

• Revert "Update MailManager.php"

This reverts commit 1a9f6c9c.

• feat: Refactor MailManager.php to improve readability and maintainability

The code changes in MailManager.php refactor the createSmtpTransport method to improve readability and maintainability. The changes include type casting for certain configuration values and use of the null coalescing operator to handle missing values. This ensures that the method creates the SMTP transport correctly.

Note: This message has been generated based on the provided code changes and recent commits.

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Co-authored-by: Deeka Wong 8337659+huangdijia@users.noreply.github.com