When is the best time not to send an e-mail message? Return Path, an e-mail forwarding service, has analyzed the results of more than 16,000 of its clients’ campaigns (mailings that people actually wanted, like sales notices) to see how many of the messages were stopped by spam blockers or filed into spam folders. The results?

Mass messages sent between 10 a.m. and 2 p.m. on Saturday and Sunday are almost 10 percent less likely to reach their intended recipient.

George Bilbrey, vice president for deliverability services at Return Path, said that most Internet service providers use content-based filters that look at a number of factors to determine the deliverability of a message, including when it was sent: ‘‘Spammers tend to send spam at certain times of day or days of week more than others, and the blockers pick up on that.’’

Generally, the worst times to send messages are when e-mail traffic is highest. As on weekends, the worst time during weekdays is 10 a.m. through 2 p.m. ‘‘Much like driving to work on a busy day,’’ Mr. Bilbrey said, ‘‘if there are a lot of cars on the road, it will be harder to get where you’re going.’’

More here.