sorry for this late answer.
Here is the diagnostic test report :
Mailer: postsmtp
HostName: sitea2n.fr
cURL Version: 7.74.0
OpenSSL Version: OpenSSL/1.1.1w
OS: Linux info 3.0 #1337 SMP Tue Jan 01 00:00:00 CEST 2000 all GNU/Linux
PHP: Linux 8.2.24 C.UTF-8
PHP Dependencies: iconv=Yes, spl_autoload=Yes, openssl=Yes, sockets=No, allow_url_fopen=Yes, mcrypt=No, zlib_encode=Yes
WordPress: 6.6.2 fr_FR UTF-8
WordPress Theme: materialischild
WordPress Plugins: Post SMTP, PDF Embedder Premium, Add Categories to Pages., Adminimize, Akismet Anti-spam: Spam Protection, amr users, Activity Log, Code Snippets Pro (Premium), Code Snippets, Colorlib Login Customizer, Contact Form 7, CookieYes | GDPR Cookie Consent, DCO Comment Attachment, Decent Comments, Elementor Pro, Elementor, Enable Media Replace, Essential Addons for Elementor, WP File Manager Google Drive, Folders Pro, Formidable Forms Pro, Formidable Visual Views, Formidable Forms, Google Analytics for WordPress by MonsterInsights, Image Optimizer - Compress, Resize and Optimize Images, Solid Security Pro, Materialis Companion, Members, Notification : Conditionals, Notification, Smart Slider 3, SiteOrigin CSS, Easy Updates Manager Premium, Subscribe to Comments Reloaded, Ultimate Member, Ultimate Member - Online, UpdraftPlus - Backup/Restore, When Last Login - Export User Records, When Last Login, WP Cleaner Pro, WP Crontrol, WP File Manager - PRO, WP Import Export Lite, WP-Optimize - Clean, Compress, Cache, WPS Hide Login
WordPress wp_mail Owner: /homepages/41/d764886830/htdocs/clickandbuilds/WordPress/Sitea2n1/wp-content/plugins/post-smtp/Postman/PostmanWpMailBinder.php
WordPress wp_mail Filter(s): wp_staticize_emoji_for_email, PostsmtpMailer->get_mail_args
WordPress wp_mail_from Filter(s): BracketSpace\Notification\Integration\WordPress->filter_email_from_email
WordPress wp_mail_from_name Filter(s): BracketSpace\Notification\Integration\WordPress->filter_email_from_name
WordPress phpmailer_init Action(s): wpcf7_phpmailer_init
Postman: 2.9.9
Postman Sender Domain (Envelope|Message): gmail.com | gmail.com
Postman Prevent Message Sender Override (Email|Name): Yes | Yes
Postman Active Transport: API Gmail (https:login://www.googleapis.com:443)
Postman Active Transport Status (Ready|Connected): Yes | Yes
Postman Deliveries (Success|Fail): 188785 | 172
Postman Email Log (Enabled|Limit|Transcript Size): Yes | 1000 | 128