Frankly I wouldn't do it quite like that. First I would use the function referred to in the comment at the start of the code below to open Outlook correctly. You can then use the Word Editor to edit the message body and retain the default signature.
I have made some changes to your code to get the ID number from the CC to eliminate the pasting.
Code:
Option Explicit
Private Sub CommandButton1_Click()
'Graham Mayor - https://www.gmayor.com - Last updated - 14 Jan 2021
'Requires the code from http://www.rondebruin.nl/win/s1/outlook/openclose.htm
'to either retrieve an open instance of Outlook or open Outlook if it is closed.
Dim strPath As String, sID As String
Dim OL As Object
Dim olInsp As Object
Dim oDoc As Document, wdDoc As Document
Dim oRng As Range
Dim EmailItem As Object
sID = GetCC
If sID = "" Then Exit Sub
strPath = Environ("UserProfile") & "\Desktop\"
Set oDoc = ActiveDocument
oDoc.SaveAs2 FileName:=strPath & "CCB Proposal Submission ID # " & sID & ".docx", FileFormat:=wdFormatXMLDocument
Application.ScreenUpdating = False
Set OL = OutlookApp
Set EmailItem = OL.CreateItem(0)
MsgBox "Your CCB proposal document has been saved to your desktop as 'CCB Proposal Submission ID # " & sID & "'." & vbCr & vbCr & _
"Click 'OK' to open your submission email draft."
With EmailItem
.Subject = Left(oDoc.Name, InStrRev(oDoc.Name, ".") - 1)
.To = "NAME_REDACTED"
.CC = "NAME_REDACTED"
.Attachments.Add oDoc.FullName
.BodyFormat = 2 'olFormatHTML
Set olInsp = .GetInspector
Set wdDoc = olInsp.WordEditor
Set oRng = wdDoc.Range
oRng.Collapse 1
oRng.Text = "Greetings," & vbCrLf & vbCrLf & _
"Attached please find a CCB proposal submission." & vbCrLf & vbCrLf & _
"Please let me know if you have any questions." & vbCrLf & vbCrLf & _
"Thank you."
.Display
End With
Application.ScreenUpdating = True
Set oDoc = Nothing
Set OL = Nothing
Set wdDoc = Nothing
Set oRng = Nothing
Set olInsp = Nothing
End Sub
Private Function GetCC() As String
Dim oCC As ContentControl
For Each oCC In ActiveDocument.ContentControls
If oCC.Title = "SubmissionIDNo" And oCC.Tag = "SubmissionIDNo" Then
If oCC.ShowingPlaceholderText = True Then
MsgBox "Enter the SubmissionIDNo"
oCC.Range.Select
GoTo lbl_Exit
Else
GetCC = oCC.Range.Text
End If
Exit For
End If
Next oCC
lbl_Exit:
Set oCC = Nothing
Exit Function
End Function