to replicate issue:
-log into acloud crm
-select existing contact or create new
-when in contact record scroll down to Activities sub section
-select the create task drop down menu
-then select compose email
-can enter subject and email message
-select the attach button
-ensure the attach tab is select and select 'add files' button
this issue occurs in both i.e 11 and Chrome.
if sending standard email from main account and attaching files works fine.