You can solve the problem of attachments being stripped from your “Sent” folder by simply adjusting your Horde preferences.
1) Login to cPanel.
2) Navigate Email accounts.
3) Login to the email account via horde Webmail Application
4) Click on “Settings” and then click on the “Preferences”.
5) Again click on the “Mail” box.
6) Navigate to “Sent Mail” under the section “Compose”.
7) Change the option “Save attachments in the sent-mail message?” to “Save attachment” and click “Save” button.
Now the error should be fixed and you should able to see the attachment file in the sent items.
If you need any further assistance please contact our support department.