Combining cells from Sheet A to sheet B (split up text)

Hi. Welcome to the forum.

I copied sheet B into a new tab in Sheet A and renamed it DocumentB, just to make it easier.
Then I use this formula in cell D2 and drag it across and down:

Formula:

=IFERROR(INDEX(DocumentB!$F$1:$F$1000,AGGREGATE(15,6,ROW($A$1:$A$1000)/(DocumentB!$C$1:$C$1000=$C2),COLUMNS($A$1:A$1))),"")

You can use the formula changing the references to a different workbook, but probably both workbooks must be open so the formula works.

Please check wb attached and let us know how it goes.

Good luck!

Hello, j.88. Sorry for the delay.

The INDEX function here will find a value, according to specified column and row, in this case it is only one column (F), so only the row is to be found. That job is taken care of by the AGGREGATE, ROW and COLUMNS functions combined.
In the formula bar, if you select the argument ROW($A$1:$A$1000)/(DocumentB!$C$1:$C$1000=$C2) and press key F9, you'll see a list with several error values and the numbers 2, 3, 4, indicating that the relevant values are in those rows.

As the subfunction SMALL is selected in the AGGREGATE function (No. 15), that subfunction finds the Nth small value in the array created with that argument above (ROW($A$1:$A$1000)/(DocumentB!$C$1:$C$1000=$C2)), ignoring error values (2nd argument in the AGGREGATE function (No. 6)).

COLUMNS($A$1:A$1) is k, the last argument in the AGGREGATE function and returns 1, i.e., the first small, or smallest relevant value, in this case row 2. As you drag the formula across, this k becomes COLUMNS($A$1:B$1) and returns 2, the second relevant value, in this case row 3, and so on.
When you drag to formula down, it will refer to the second relevant value, that is, the second e-mail.

I hope this helps you clarify how the formula works.

Thank you for the feedback and for the reputation added.

Have a blessed day.