Why Did Some Bulk Send Recipients Fail?

A handful of failures in a big campaign is normal — lists age, people leave companies, typos slip in. Here's what each failure means and the fix. 

The Failure Types 

1.  Invalid email — the address was malformed in the CSV (missing @, bad domain). Fix the row. 

2.  Bounce — the address is well-formed but the mailbox doesn't exist or is full. Get a current address. 

3.  Duplicate — the same email appeared twice; only the first instance was sent. No action needed unless they were meant to be different people. 

Recovering 

1.  In the campaign view, filter to failed recipients. 

2.  Correct the addresses. 

3.  Re-send to just the failed rows — the successful sends are untouched; nobody gets a confusing second copy. 

Tip: Failure rate above a few percent? Your source list is stale — worth a cleanup pass before the next campaign rather than after.