The problem is that it's "badly formed" CSV data - not the pipe character instead of comma, but the lack of double quotes to delimit multiline strings.
When you want to use "broken strings", you have to use double quotes around all string elements:
unique_id|name|notes
123|"John"|"Subject: Meet the new interns
Dear team,
I'm happy to inform you of the commencement of our summer internship program. We recruited 10 interns"
456|"Rit"|"Subject: Meet the new interns
Dear team,
I'm happy to inform you of the commencement of our summer internship program. We recruited 10 interns"
Otherwise the reader has no idea where the column data is meant to end - is it meant to be
"123"
"John"
"Subject: Meet the new interns
Dear team,
I'm happy to inform you of the commencement of our summer internship program. We recruited 10 interns"
"456"
"Rit"
"Subject: Meet the new interns
Dear team,
I'm happy to inform you of the commencement of our summer internship program. We recruited 10 interns"
Or
"123"
"John""Subject: Meet the new interns
Dear team,
I'm happy to inform you of the commencement of our summer internship program. We recruited 10 interns
456"
"Rit"
"Subject: Meet the new interns
Dear team,
I'm happy to inform you of the commencement of our summer internship program. We recruited 10 interns"
-null-
Most (non-trivial) CSV readers support this, as well as double quotes / column separators that appear in strings.