Unsupported MIME type: message

Hi, hope you are well in this strange period.
I have a problem i can’t fix with the plugin, when testing config, all seems to be ok :

Postie Configuration Test
OS: Linux h2web190 4.9.0-0.bpo.12-amd64 #1 SMP Debian 4.9.210-1~deb8u1 (2020-02-21) x86_64
PHP version: 7.3.16
PHP error_log: 
PHP log_errors: On
PHP get_temp_dir: /home/clients/f220f52d6747ea3ebb2f854ced2ff8fc/tmp/
PHP disable_functions: set_time_limit,passthru,exec,system,popen,shell_exec,proc_open
PHP cURL version: 7.52.1
MySQL Version: 5.7.29
WordPress Version: 5.4
WordPress Singlesite
WP_TEMP_DIR: (none)
WP_HOME: (none)
home_url(): https://catherinelauper.ch
WP_SITEURL: (none)
site_url(): https://catherinelauper.ch
WP_DEBUG: Off
WP_DEBUG_DISPLAY: null
WP_DEBUG_LOG: Off
WP_MAX_MEMORY_LIMIT: 256M (default)
WP_MEMORY_LIMIT: 640M
imagick version: 3.4.4
gd version: 7.3.16
image editor supported: WP_Image_Editor_Imagick
WP_Image_Editor_Imagick supports: image/jpeg
WP_Image_Editor_Imagick supports: image/png
WP_Image_Editor_Imagick supports: image/gif
image editor supported: WP_Image_Editor_GD
WP_Image_Editor_GD supports: image/jpeg
WP_Image_Editor_GD supports: image/png
WP_Image_Editor_GD supports: image/gif
Registered image sizes
image memory limit: 640M
DISABLE_WP_CRON: Off
ALTERNATE_WP_CRON: Off
WP_CRON_LOCK_TIMEOUT: 60
iconv: present
Active plugins
     captcha-code-authentication/wpCaptcha.php => 2.7
     divi-children/divi-children.php => 3.0.9
     duplicate-post/duplicate-post.php => 3.2.4
     instant-images/instant-images.php => 4.3.1
     loginpress/loginpress.php => 1.4.3
     mailpoet/mailpoet.php => 3.46.10
     postie/postie.php => 1.9.46
     really-simple-ssl/rlrsssl-really-simple-ssl.php => 3.3.1
     supreme-modules-for-divi/supreme-modules-for-divi.php => 2.1.0
     updraftplus/updraftplus.php => 1.16.23
     wp-super-cache/wp-cache.php => 1.7.1
Postie is in /home/clients/f220f52d6747ea3ebb2f854ced2ff8fc/web/wp-content/plugins/postie/
Postie Version: 1.9.46
POSTIE_DEBUG: Off
Clock
This shows what time it would be if you posted right now

Wordpress timezone: Europe/Zurich (2)
Current time: 2020-04-16 11:09:18
Current time (gmt): 2020-04-16 09:09:18
Postie time correction: 2
Post time: 2020-04-16 11:09:18
Encoding
default_charset: UTF-8
DB_CHARSET: utf8
DB_COLLATE: database default
WordPress encoding: UTF-8
Connect to Mail Host
Postie connection: sockets
Postie protocol: pop3
Postie server: mail.infomaniak.com
Postie port: 110
Successful POP3 connection on port 110
# of waiting messages: 26

But when i click the Process Email button i have an error message and i receive this from my mail host :

This message has been sent from https://catherinelauper.ch. You can disable or control who receives them by changing the Postie 'Notify on Error' setting. 

5e981f6660504 has an unsupported MIME type message and was not added. 
Supported types: 

I’ve searches every where i cant’t find the solution… 🙁
If you could help me it would be fantastic 🙂
Thanks a lot,
Fred