The fact that macro security was set to high would not prevent code
from workbooks that were loaded at startup (e.g. addins and files in
XLSTART) from running. Hence my suggestion of opening Excel with the
shift key held down to see if the behaviour went away and could
therefore be attributed to some malicious code.

If you have further trouble with the sheet I think I would remake it
(by copying the data and paste special / values to a new workbook, then
using the second macro to set the mailto hyperlinks that you really
want.

Bill Manville
MVP - Microsoft Excel, Oxford, England
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