You are using Signature Manager Exchange Edition to append professional email signatures to messages sent from Microsoft Outlook and mobile devices.
You have removed existing Microsoft Outlook signatures (as per this Knowledge Base article) but you also need to remove the default ‘Sent from iPhone’ signature for iPhone users (or similar default messages for other devices).
Exclaimer Signature Manager Exchange Edition cannot remove content
from the message body. Since mobile devices cannot be easily managed from the
Active Directory domain, these default signatures should be removed from
Customer support service by UserEcho