Spamjadoo
Rejection versus scanning.
Traditional spam filters accept a message, scan its content, and score it after acceptance; Spamjadoo rejects unwanted mail during the SMTP handshake, before the message body is ever received. This is a comparison of two architectures, not of vendors.
The two architectures
A content filter is a classifier. It receives the whole message, extracts features, produces a score and compares it to a threshold. The better the classifier, the fewer mistakes, but every message must be received and scored, and every mistake sits in a quarantine.
A handshake-level gateway is a policy engine. It asks a sequence of yes-or-no questions during the SMTP dialogue, each answered by a fact it can look up: is this IP listed, does it have reverse DNS, does the sender domain's SPF allow this server, does the recipient exist, is this alias open to this sender. The first no ends the session with a 550. Only mail that gets a yes to everything is received, and only that mail is scored by the classifier.
Side by side
| Content-scanning filter | Spamjadoo | |
|---|---|---|
| When the decision is made | After the whole message is received | During the SMTP session, before DATA where possible |
| What a rejected message costs the receiver | Bandwidth, storage, scanning CPU, quarantine review | A few DNS lookups and a one-line reply |
| What the sender learns | Nothing (silent drop or quarantine) | A 550 with the reason, in their own bounce |
| False positives | Depend on a score threshold; live in quarantine | Tied to a verifiable fact; visible to the sender |
| Backscatter | Possible when accepted mail is bounced later | Impossible: unknown recipients refused at RCPT TO |
| Directory harvest attacks | Detected by content or volume after acceptance | Cut off after a few invalid recipients |
| Content scanning | On 100% of traffic | On the fraction that passed the handshake |
| Per-recipient policy | Usually per domain or per server | Per user, per alias, per group |
Where content scanning still wins
A compromised account at a reputable provider passes every handshake check, because the sending server genuinely is authorised. Phishing from such accounts is caught by content analysis, URL reputation and, increasingly, by the recipient's own judgement. That is why Spamjadoo includes a classifier and antivirus at DATA. The argument is about order, not about replacing one with the other.
How to test the claim
Put Spamjadoo in front of your existing filter for a month. Count what the existing filter receives before and after. Its quarantine will shrink, and what remains in it will be the hard cases that deserve a human look.