E-mail Madness

My mailbox is getting slammed. Like most businesses we receive a fair amount of e-mail solicitation, it is definitely increasing. Typically I deleted one message for every two that I opened. Now I'm deleting at least two for every message that I read.
I'm deleting them unopened.
It seems many businesses are stepping up their e-mail campaigns, but is it effective? In my case the increase in e-mail solicitation is having a negative effect. Before I would glance through some of the more interesting subject lines, now if I wasn't expecting it, I'm deleting it. This past weekend I discarded 78 unsolicited e-mails and saved one. That's less than a one and one half percent effectiveness for unsolicited e-mail. If you were paying postage on these e-mails would you be getting the ROI you needed to continue sending them out?
If you are sending out e-mails to drum up sales, don't mail me on the weekend. You stand a much better chance of having me read it if I get it on a Wednesday or Thursday.