|How about this:|
=MID(A1, FIND("[",A1)+1, FIND("]",A1)-FIND("[",A1)-1)
MID(text, start_num, num_chars)
The start_num is determined by FIND("[",A1)+1 which returns the location of the first character after the [
num_chars is determine by FIND("]",A1)-FIND("[",A1)-1 which returns the number of characters between the [ ] based on the location of the [ ] in the referenced cell.
You could then do an Edit...Copy...PasteSpecial values.
Another option is to do a Data...Text to columns...Delimited on the [
This will return firstname.lastname@example.org]
The do an Edit...Replace ] with nothing, Replace all.
Either way, it's a 2 step process.