The mail has to get to you somehow. The way SMTP works is that there are two places your email address is usually used during email delivery:
1. Before the actual sending of the mail data, the sending server connects to your mail server and after a polite introduction sends 'RCPT TO: xxxx@yyyy.com'. This is where your unique-for-that-site email address is used.
2. Later on during the transmission, all the 'real' mail headers are sent, and this is where the To, From, Subject, and CC headers are set. If you were BCC'd there is no 'BCC' header, so the 'To' header normally has the mail address of the original 'To' recipient. Or in a lot of cases the 'To' header is omitted entirely. Depending on your mail client, you will either see your name in the To field, or something like 'Undisclosed Recipients'.
Spammers typically shake it all up, so that the 'To' header rarely matches the 'RCPT TO:' value.
In my bespoke anti-spam system, I re-inject the 'RCPT TO:' and 'MAIL FROM:' into the mail headers (prefixed with X-) so i can easily see in my client what is actually going on.
1. Before the actual sending of the mail data, the sending server connects to your mail server and after a polite introduction sends 'RCPT TO: xxxx@yyyy.com'. This is where your unique-for-that-site email address is used.
2. Later on during the transmission, all the 'real' mail headers are sent, and this is where the To, From, Subject, and CC headers are set. If you were BCC'd there is no 'BCC' header, so the 'To' header normally has the mail address of the original 'To' recipient. Or in a lot of cases the 'To' header is omitted entirely. Depending on your mail client, you will either see your name in the To field, or something like 'Undisclosed Recipients'.
Spammers typically shake it all up, so that the 'To' header rarely matches the 'RCPT TO:' value.
In my bespoke anti-spam system, I re-inject the 'RCPT TO:' and 'MAIL FROM:' into the mail headers (prefixed with X-) so i can easily see in my client what is actually going on.