Encontrou uma maneira de usar: Open mailbody For Input As #1
e, em seguida, Line Input #1
Sub Mail_LSP(mailsubject As String, consignee As String, coalcopy As String, mailbody As String)
Dim mlook As Outlook.MailItem
Dim linecontent As String
Dim mailcontent As String
Open mailbody For Input As #1
Do Until EOF(1)
Line Input #1, linecontent
mailcontent = mailcontent & vbNewLine & linecontent & vbNewLine
Loop
Close #1
Set mlook = Outlook.Application.CreateItem(olMailItem)
mySubject = mailsubject
mlook.To = consignee
mlook.CC = coalcopy
mlook.Subject = mailsubject
mlook.Body = mailcontent
mlook.Send
End Sub