Why does VBA editor open Outlook?

Question

Sometimes, when I check some variable on my excel macro, Outlook opens by itself. This is pretty annoying since I am not even using Outlook and not configured. What's going on here?

I am using Office 2016.

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Edit: I don't think this is due to the actual macro, but anyway, here it is:

Sub duplicateSheets()
    Dim i As Integer
    For i = 1 To 3
        ThisWorkbook.Sheets("classes").Copy _
            After:=ThisWorkbook.Sheets(ThisWorkbook.Sheets.Count)

        ThisWorkbook.Sheets("pivot").Copy _
            After:=ThisWorkbook.Sheets(ThisWorkbook.Sheets.Count)
    Next
End Sub

Outlook opens when I check ThisWorkbook.Sheets("classes").

Answer 1

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