The events herein took place a couple of months ago. My rage has subsided into a background hum of frustration. Only now can I write about the experience.
My parents' ISP uses some wonderful spam software that they won't describe to anyone. (Repeated requests for some type of guidance on how it works (so that it can be worked with) were met with only vague generalities and wildly divergent stories (all "confirmed" with a supervisor))
The upshot is that their customer service tells you you can send about 25-35 emails per hour (depending on which customer service rep you talk to) without really worrying about it, but that any more than that needs to be manually broken up and sent individually over the course of a day or more. There's been talk of a cunning "points-based" algorithm on web boards.
If you get it wrong, they block you from using email for x hours (again, they're not able to explain how many hours they block for, but it's "3", "6" or "24" depending on the rep).
Their T's and C's allow them to "interfere" with email if it could in some way affect the performance of their network. Sure.
And their system doesn't actually do what sane people would expect (accept the message, delay delivery, trickle them out, prompt the user with a turing test to allow immediate delivery or *something* that doesn't inconvenience the user so much) so that busy people can just send an email and run - it actively rejects connection attempts once a certain limit is hit, and starts adding "ban time".
As for how I found this out: my parents recently moved back from the US, and wanted to send a quick email to everyone telling them of their new email address.
This would have been a one-off mailing to about 90 recipients. They'd done it before (from their US ISP, when moving out there), and they simply wanted to do it again.
Nope. Outlook just hung when trying to send the message.
After protracted (and heated) discussions with the ISP helpdesk, their solution was:
0) Disable the XP SP2 firewall (a false start, you might say - of course, this made no difference to the problem).
A) you've been banned for 6 hours. Wait that long and try again.
B) When you try again, break the message up into chunks of 20-30 people, send one message, then come back after an hour, and send the next message, and so on, and -very importantly- DO NOT UNDER ANY CIRCUMSTANCES try to re-send the message if it fails, as you'll be banned for longer.
They suggested that some email client or another could do this without needing the user to stay at the keyboard (they named Outlook Express and Outlook) but when challenged, rescinded that with a "well we don't support Outlook anyway". They gave a manual "Copy the contents and re-paste them into a new email to the next batch of recipients" workaround. Because that's what you're paying for on a residential plan.
So essentially, if you need to send to a large number of people, you are SOL (that means "out of luck", mum) with this ISP, unless you can keep coming back to your computer every hour to repeat a manual copy-paste-select-new-recipients process to send an email. I mean, computers are meant to save people time!? There are any number of possible solutions to this (authenticated outbound SMTP, published "hard limits" on a number of messages/recipients per day, Turing tests, the works? They all deal with the virus-with-SMTP-engine issue, leaving spammers a) authenticating, and b) unable to spam as many folk) but the worst of all possible worlds seems to have been picked.
This is their solution to the spam and virus problem.
Of course, if you're a commercial spammer and pay for the privilege on their business plan, you can use a different mail server that doesn't do the outbound email filtering.
Post-note: "Why not change ISP's?" - this is essentially the only broadband ISP available in their area at the moment.