One message -- many people

 

 From: woodyswatch.com

Don't use TO or CC for sending to groups of people who don't know each other. These days that is considered poor email etiquette. That?s because everyone who gets the email can see the email addresses of all the other recipients which could be considered a breach of privacy these days.

There's a more serious concern to do with spam and viruses. There are many email worms that search an infected hard drive for email address to send infected emails. Those worms can check not just the contacts list but also the history of received emails for new targets.  This doesn't really apply when you're sending messages to a small group of people who know each other, but caution is polite and prudent when the receivers are a disparate group who don't know each other.

If you send a email with a large TO or CC list to an infected computer then all those recipients are in the firing line to a new round of nasties.

Better to use BCC - Blind Carbon Copy - but this has its own disadvantages -- messages with BCC's are more likely to be considered spam. Emails sent directly to one person are, contra wise, less likely to be marked as spam.

BCC is quick and usually quite efficient. The BCC receivers should not see the email addresses of their compatriots (just anyone in the TO or CC fields).

We have heard the urban myth that the list of BCC recipients is actually hidden in each copy of the message and can be found by worms. This is plain wrong and looking at the message header on a BCC received message would show. The BCC recipients are stripped out when the email is relayed to each individual mailbox.