Sunday sees the second-highest amount of mass-marketing emails opened, the anti-virus firm said.
According to a survey conducted by email mass marketer ExactTarget, 92 percent of all emails - and 96 percent of all campaign emails - are sent during the workweek. However, while Sunday sees only three percent of all sent emails, links in those messages are most likely to be clicked then.
"This may be due to the fact that users receive much less spam over the weekend, so they are more inclined to click on links, something they would do less frequently during the week given the larger volume of email received," Konstantin Kornakov said on the Kaspersky Viruslist site. "This theory is also supported by findings that smaller mailing lists tend to have better opening and clicking rates."
Mass mailings to 100 recipients or less have an opening rate of more than 28 percent, according to the study. Yet much larger email lists – more than 100,000 – show a sharp decline in openings, with a rate of just better than 18 percent.
The survey also showed that about 40 percent of spam marketing emails are actually opened, and only 0.25 percent of recipients used unsubscribe services in 2005.
"This can be proof of the fact that most people now see spam and unsolicited emails as part of the actual fabric of the internet and something that can not be fought against," Kornakov said.
The study, conducted throughout 2005, surveyed more than 4,000 organizations and 2.7 billion emails from 230,000 mailings, Kaspersky said.
Shane Coursen, senior technical consultant at Kaspersky, said Monday that the study also showed seasonal trends for opened spam emails, including a peak season from October to the end of the year.
"There were higher opening rates from October until December," he said. "People are online and they're buying presents. And of course they're also doing some research on what they're going to buy."