Concatenate formula Nested within a IF formula is not producing expected results.

I am trying to use a combination of Concatenate and IF formula to produce an email.

My input.

D4: First Name:
D5: Middle Name:
D6: Last Name:

D8: Organization:

Once all these are filled, I want the formula to produce a result like

FirstName.M.LastName@Organization.com

I have used the following formula.

Formula:

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Problem is if there is a middle name the formula works fine, but in case where there is no middle name, it produces the following result.

FirstName..LastName@Organization.com

Please advice how do I remove the additional (.) in cases where there is no middle name.

Try

Formula:

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try
=SUBSTITUTE(TRIM(D4&" "&D5&" "&D6&" ")," ",".")&"@"&D8