Otdfbt

I created a transport-rule in our Exchange server 2013 where it will add a warning text on top of email-body to all external incoming emails. This is to alert employees about potential risks in external emails when it has website-links and attachments which may be harmful. The text is as follows:
Text

CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe.

Now, when user will reply to the email, I want it to be remove when Exchange process it to send. How can I remove the warning text from outgoing emails in Exchange? I was looking for something in rules, but there is none I could find.

Any help will be appreciated. Thanks.

There is no such rule. The MS Exchange transport rules can only add such a string but couldn´t remove them.

I would do the following:

• Setup a Proxy (Squid and SquidGuard or something like that)


• Start using an GPO which block the attachments you would see as "non secure" as written here
  

How to remove the yellow caution bar (not why, or if you should)
In Outlook, press alt + F11 (to open Microsoft VBA)

Paste the following into ThisOutlookSession:

Option Explicit

Sub InsertHyperLink(MyMail As mailItem)

 Dim body As String

 body = MyMail.HTMLBody

 body = Replace(body, "background-color:#FFEB9C; width:100%; border-style: solid; border-color:#9C6500; border-width:1pt; padding:2pt; font-size:10pt; line-height:12pt; font-family:'Calibri'; color:Black; text-align: left;", "", 1, 1, vbTextCompare)

 body = Replace(body, "CAUTION:", "", 1, 1, vbTextCompare)

 body = Replace(body, "This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe.</div>", "", 1, 1, vbTextCompare)

 MyMail.HTMLBody = body

 MyMail.Save

End Sub

Edit the registry and add the following DWORD

HKEY_CURRENT_USERSoftwareMicrosoftOffice15.0OutlookSec‌​urity DWORD: EnableUnsafeClientMailRules Value: 1

Enable all macros in Trust Center (or sign this one)

Create a Custom Rule executing the macro

File / Manage Rules & Alerts / New rule / "Apply rule on messages I receive"/ "Run a script" / Click on the text that says "a script" / “ThisOutlookSession”

Test, Done!