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Customers frequently face the issue of having unnecessary or irrelevant content being added as comments a comment from a reply email to a particular issue.
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This is the classical split regex approach which attempts to split the email body based on how various email clients format reply emails.
It is easy to see that mail clients format reply emails differently that which makes splitting difficult and prone to errors.
Here are two examples of the two most widely used email clients (Gmail and MS Outlook), the red frames mark the expressions people usually try to match when wanting to use regular expressions.
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