Every bulk upload is logged. Import history is the answer to "where did these contacts come from" and "did that file actually work".

#What each entry shows

Field	Means
File name	What you uploaded
Total records	Rows in the file
Imported	Contacts successfully created
Failed	Rows that did not make it, with the reason
Auto-generated values	Contacts imported with a placeholder name or email
Completed	When it finished

#Getting there

From Accounts → Import History, or by clicking View Details on the notification you get when an import finishes.

#What to check after an import

1
Does imported plus failed equal your total?
If not, and your file was over 2,000 rows, the rest was left behind. See Bulk upload.
2
How many have auto-generated values?
Those are the ones with placeholder emails, which cannot receive email until fixed.
3
Read the failures.
They are usually one systematic problem rather than many individual ones.

It is an audit trail, not a cleanup tool

History records what happened. To fix contacts, edit them from Accounts. To undo a bad import, you delete the contacts, there is no bulk rollback.

Check before re-uploading

If an import looks like it failed, look here first. Re-running a file that partly succeeded creates a second copy of everything that worked, with new unique addresses for each collision.