Process bounces and spam complaints
Connect bounce and feedback-loop mailboxes or provider callbacks so bad recipients stop receiving mail.
Mailbox handlers
Bounce handlers read delivery-failure notices from an IMAP or POP mailbox. Feedback-loop handlers read ISP spam-complaint notices from a dedicated mailbox.
- Host, username, password, port
- Mailbox connection credentials.
- Method and encryption
- IMAP or POP access with the required SSL/TLS behavior.
- Validate certificate
- Controls mailbox TLS certificate validation.
- Delete after processing
- Removes handled notices from the mailbox.
Alternative provider callbacks
Mailgun, SendGrid, MailJet, Elastic Email, SendinBlue, and Amazon SES can send delivery reports directly to K2Mailer callback routes. This reduces reliance on parsing mailbox notices.
Why bounce and complaint processing protects deliverability
Every mailbox provider watches how a sending domain handles bounces and spam complaints. If bounced addresses keep receiving mail and complaints are never removed from active lists, inbox providers read that as a signal of poor list hygiene and begin routing future campaigns to the spam folder, even for engaged recipients.
Processing bounces and feedback-loop complaints promptly, and connecting that data to suppression and blacklists, keeps your sending reputation clean. This is one of the most direct levers you have over long-term inbox placement, alongside authenticated sending domains and a properly configured sending server.
Choosing between mailbox parsing and provider callbacks
Mailbox-based bounce and feedback-loop handlers work with any IMAP or POP inbox, which is useful if your sending domain already has a dedicated bounce or abuse mailbox configured with your registrar or mail host. They do add a small delay, since notices are only processed when the mailbox is checked.
Provider callbacks from services like Mailgun, SendGrid, MailJet, Elastic Email, SendinBlue, or Amazon SES report bounces and complaints to K2Mailer in close to real time, which is generally the more reliable option when your sending infrastructure already runs through one of those providers. Where both are available, provider callbacks are the better default and mailbox parsing works well as a backup.
Frequently asked questions
- Do I need both a mailbox handler and a provider callback?
- No, though some senders keep a mailbox handler as a backup while relying on provider callbacks as the primary source.
- What counts as a hard bounce versus a soft bounce?
- A hard bounce indicates a permanent failure such as an invalid address, while a soft bounce is typically temporary, such as a full inbox.
- Where does processed bounce data go?
- It feeds directly into suppression and blacklists so affected addresses stop receiving future campaigns automatically.
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