Not every bounce means the same thing.
If you treat temporary delivery issues the same way you treat dead addresses, you make bad cleanup decisions. If you ignore hard bounces, you hurt reputation and waste sends.
Hard bounces
A hard bounce is usually a permanent failure.
Common reasons include:
- mailbox does not exist
- domain does not exist
- address is malformed
The important part is the action: these addresses usually should not stay in future sends.
Soft bounces
A soft bounce is usually temporary.
That can happen because of:
- a full inbox
- a temporary server issue
- message-size limits
- short-term throttling
A soft bounce is frustrating, but it does not automatically mean the address is bad forever.
Why the distinction matters
Hard bounces are a stronger negative signal for sender reputation because they suggest poor list quality.
Soft bounces still matter, but they usually call for monitoring and retry logic, not immediate removal.
The practical response
- remove or suppress addresses that hard-bounce
- monitor repeat soft bounces across sends
- clean your list before campaigns so obvious hard-bounce candidates never get sent in the first place
Where MailCull fits
MailCull helps on the prevention side.
It catches many of the issues most likely to create hard bounces later:
- broken syntax
- typo domains
- disposable providers
- domains without viable mail setup
That does not eliminate every delivery problem, but it reduces the avoidable ones before they hit your campaign report.