How relay email processing differs from aliases
Cleanbox handles email through two distinct delivery paths: aliases (IMAP upload) and relay (SMTP forward). Both share the same spam detection and evaluation chain, but they differ in how email reaches your inbox.
Delivery method
| Aliases | Relay | |
|---|---|---|
| Delivery protocol | IMAP (upload to mailbox) | SMTP (forward to your server) |
| Credentials needed | IMAP login for your mailbox | SMTP destination hostname + port |
| Folder control | Cleanbox chooses IMAP folder | Your server handles folder routing |
| IMAP flags | Cleanbox sets \Seen, \Flagged | Not applicable |
| Delivery failure | Status: failed. Manual retry. | Automatic retry queue (up to ~4 days) |
SPF handling
Aliases: Cleanbox delivers via IMAP, so SPF is not relevant at delivery time. Your mailbox provider does not check SPF on IMAP uploads.
Relay: Cleanbox forwards via SMTP. Your server may check SPF on incoming connections. To ensure SPF passes, Cleanbox uses SRS (Sender Rewriting Scheme) to rewrite the envelope-from to an @srs.cleanbox.to address. Your server checks SPF against this domain (which passes) instead of the original sender.
Virus scanning
Aliases: No virus scanning. Rspamd content analysis is the primary protection.
Relay: ClamAV virus scanning is included. Every relay message is scanned for malware before forwarding. If a virus is detected, the message is rejected immediately.
Filter differences
Aliases: Filters support both allow and deny actions. Allow filters can include delivery options: store in a specific folder, mark as read, mark as flagged, forward to another address.
Relay: Filters only support the deny action. Since Cleanbox does not control the destination mailbox on relay (your server does), delivery options like folder routing do not apply.
Shield availability
Aliases: Full Shield support — rate limiter, delivery snoozer, and gatekeeper.
Relay: Shield is not available on relay addresses. The protection layer for relay addresses consists of DNSBL checks, spam thresholds, contact states, and filters.
What is shared
Despite the delivery differences, aliases and relay addresses share:
- Same spam engine — Rspamd analysis with Bayes classifier and Cleanbox reputation symbols
- Same contact system — Contacts, states, categories, and unsubscribe work identically
- Same evaluation chain — Contact blocked → shield → spam → filters → contact state → delivery
- Same message storage — Both store metadata + raw email in cloud storage for the retention period
- Same dashboard — Messages from aliases and relay addresses appear in the same history view
