You can easily fix the problem of attachments being stripped from your “Sent” folder by simply adjusting your Horde preferences.
1) This tutorial assumes that you are already logged into Webmail.
2) Login to the email account via horde Webmail Application
3) Click on the Settings icon in the top menu, navigate to “Preferences” then click on Mail
4) Locate the “Sent Mail” under the section “Compose”.
5) Change the option “Save attachments in the sent-mail message?” to “Save attachment” and click “Save” button.
That’s it! Your preferences have been updated.
You can now send a new email with an attachment, and you should be able to see the attachments for any emails in the Sent folder.