In case if you are using a Plesk server with MailEnable as mail service, you get Horde webmail with it which is free.
Have you noticed, if you send an email from your account, the following message gets added at the bottom of your email.
“This message was sent using IMP, the Internet Messaging Program.”
Some users do not want to include this footer message in their outgoing emails considering as security threat 
This footer message can be eliminated.
Following are the steps :
Open your IIS (Internet Information Service) >>
expand Local Server >>
locate web site entry “Webmail(Horde)” >>
right click on Webmail(Horde) and select Open >>
it will open physical location of webmail >>
here navigate imp/config/trailer.txt file
trailer.txt is the file responsible to attach above footer in each outgoing mail.
Open this file in notepad and remove above message from it, save it and close.
Thats it
Above message will not be attached to your outgoing emails from now.
