Would you please mind telling how many emails do you plan to send on per day basis? May be we can help you out... Waiting you...
If the emails are opt-in , voluntary subscribers, list was not bought, the email has a working link to unsubscribe and you don't want to sell "tramadol" should be ok with most of the hosts.
I would say, go with sambahosting (www.sambahosting.com) if you want excellent service...I am having a mailing list hosted with them which send emails to 2500 users just fine...
Sorry, but 50-100K per day is so high from our perspective and the governing anti-spam policies I'd advise you to use some specialized email hosting Sincerely
Look into a company like icontact.com. It is going to cost you a lot of money to send out that many emails in a day.
I would probably use an email provider like Aweber rather than depending on your host. e-mail is ALL they do and they will get a better inbox-bounce rate than you could