### Changed:
- Improved notifications formatting and styles.
- Sendinblue rebranded to Brevo.
### Fixed:
- Explicitly set "Content-Type" header for the HTML test email.
### Fixed:
- Setup Wizard steps navigation, when going backwards.
### Fixed:
- The check if `wp_mail` function is overwritten on Windows servers.
### Changed:
- Removed MailPoet from the list of conflicting plugins.
### Fixed:
- PHP warning for undefined variable when using the Default (none) mailer.
### Added:
- Alerts for failed emails (Email, Slack, SMS, and Webhook notifications).
- Check if `wp_mail` function is overwritten.
- DB table (`wpmailsmtp_tasks_meta`) cleanup after scheduled actions execution. Keeps DB size small.
### Changed:
- Updated the list of conflicting plugins (added Branda and MailPoet).
- Improved WP Site Health license check.
- Improved Outlook mailer authorization flow error handling.
- Updated Action Scheduler library to 3.4.2.
- Improved Amazon SES (added support for V2 client).
### Fixed:
- SMTP.com mailer email content-encoding.
- Amazon SES long Return-Path header encoding.
- Dashboard widget graph when there is no email logs data.
- Email Log retention period cleanup task DB table check.
- Missing Sendinblue email body WP filter.
- Chart.js library conflicts with other plugins.