create dynamic range that finds the last row and column with mixed data and blanks

I am trying to create a dynamic range that will expand to the last row and column. The data may contain blank cells in between, and will consist of dates and text. My data will start in $M$8 and will expand by columns and rows. I have tried to use the following formula: =OFFSET(Sheet1!$M$8,0,0,COUNTA(Sheet1!$M:$M),COUNTA(Sheet1!$1:$1)) but it does not work. How can I rewrite my formula to achieve the above? The last value in the image is in $T$13 "email" under Result header
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See if this works.

If you are going to use a dynamic range I would recommend a dynamic named range (DNR). Something like this. As a DNR this will not have to be array entered. You can "future proof" the $M$1:$T$200 parts, but I would not reference whole columns there.

rnge	=INDEX(Sheet1!$8:$8,MATCH("zzzz",Sheet1!$7:$7,1)):INDEX(Sheet1!$M$1:$M$200,MAX(IF(Sheet1!$M$1:$T$200<>"",ROW(Sheet1!$M$1:$T$200)-MIN(ROW(Sheet1!$M$1:$T$200))+1)))