Perché la posta elettronica inviata dal mio sito finisce nelle cartelle SPAM? [chiuso]

• Evita qualsiasi stringa simile a spam.

Most Spam checking these days is Bayesian, which means that that your message is checked using a fuzzy algorithm that tries to guess if resembles known Spam or Ham (good) messages (mainly by checking the frequency of common spam words and phrases).

• Invia singoli messaggi a ciascun destinatario anziché a copie.

It is better to send an individual message to each recipient, rather than using multiple addresses in the BCC field because many spam filters (and many ISP's) automatically flag multiple recipients as spam.

• Se possibile, invia tramite il server di posta dell'ISP anziché utilizzare un server SMTP locale.

Messages sent from a mail server running on your computer may be flagged as spam because some mail servers will try to contact the source IP of the sending server (which will fail with a local IP address).

• Prova con piccoli gruppi di e-mail.

It would appear that some of the big mail hosts such as Hotmail will recognize when an identical message is sent to a large number of subscribers at one time so you should stagger the delivery of your messages [...] to send your messages in small batches.

• Riduci al minimo l'utilizzo degli allegati.
• Assicurati che il computer che invia l'email abbia un record PTR inverso.

What's a reverse PTR record? It's something your ISP has to configure for you -- a way of verifying that the email you send from a particular IP address actually belongs to the domain it is purportedly from.

• Configura DomainKeys Identified Mail nel tuo DNS e codice.

What's DomainKeys Identified Mail? With DKIM, you "sign" every email you send with your private key, a key only you could possibly know. And this can be verified by attempting to decrypt the email using the public key stored in your public DNS records.

• Configura un record SenderID nel tuo DNS.

To be honest, SenderID is a bit of a "nice to have" compared to the above two. But if you've gone this far, you might as well go the distance. SenderID, while a little antiquated and kind of.. Microsoft/Hotmail centric.. doesn't take much additional effort.

SenderID isn't complicated. It's another TXT DNS record at the root of, say, example.com, which contains a specially formatted string documenting all the allowed IP addresses that mail can be expected to come from.

Fonti e informazioni aggiuntive:

• XeQute
• Domande frequenti su Spamassassin
• post di Jeff Atwood sul stesso argomento
• Pubblica sullo stesso argomento su ServerFault