Help! "No Subject" email automatically created when send or reply email


I got a weird problem with SuiteCRM email…

When we compose or reply an email and press send, CRM will automatically create a “No Subject” email under the dashlet of the user who sends the email. (Screenshot provided in attachment.)

The email is empty when opened and it is showing as assigned to the user who sent the email. ( Screenshot provided in attachment)

Does anyone seen this before? and where I can find the log that monitoring the email sending process in CRM?

CentOS Linux release 7.6.1810 (Core)
Apache/2.4.6 (CentOS)
PHP 7.3.3
SuiteCRM Version 7.11.2 Sugar Version 6.5.25 (Build 344)

Thank you,

You can change the email subject from here, i have shown in the screenshot. If there is something else to discuss, you can skype me.

i would like to share my experience with this issue.

my environment is docker

when i use bitnami/php-fpm:8.0 ~ 8.2, i have this issue. when i changed to bitnami/php-fpm:7.4.33, issue Disappeared