You may do everything you can to protect your private or business email address from being recognized by the address catchers:
№1:You’re only giving it away to close friends or business partners
№2:You’re not using it to register for newsletters or access to arbitrary websites
№3:You’re not posting it on your website or whois-entries
№4:You’re not using it to underwrite blog comments, forum entries or news posts
№5:You’re not using it with Microsoft Passport, AOL Screen Name Service, ICQ, IRC, WebEx, etc.
Even though, these rules cannot guarantee the sanctity of your inbox. Here is the catch:
People you entrusted your email address may be unaware of the lengths you go to protect your privacy. They may ignorantly include you in the “To:” or “CC:” lines of email they send to a larger crowd, opening your address to the public eye. Geesh!
So please be careful with the email addresses of your friends, colleagues and business partners and use “Bcc:” when sending an email to different groups of people at once.
As a side note, “Eyes only” obfuscation schemes such as “name (at) domain.dom”, “firstname.lastname@example.org” or “No_SpamName@domain.dom” are no silver bullet. They will need to get more and more sophisticated over time in order to outsmart the crawlers.