My website allows people to email interesting articles to their friends. One thing I've seen in the database is that sometimes people will send several, sometimes as many as ten articles to their friend. These get stored in the database and are emailed out using a cron job. I'm wondering, however, how the receiving ISP feels when sends ten emails addressed to one individual. Will they likely blacklist my IP address because they see that as spam? If so, then I need to change how my website works, allowing people to send multiple articles in a single email that gets sent to a friend.

Any thoughts on this would be appreciated!