My site sends out sales emails for products that have been purchased but some email providers are blocking or sending the emails to spam and they are completely valid emails that the customer is expecting to receive. This leads to more emails to me and some unhappy people

Hotmail - for some people the email will immediately bounce back to me with the message: "Mail rejected by Windows Live Hotmail for policy reasons. Reasons for rejection may be related to content with spam-like characteristics or IP/domain reputation problems. "

Gmail - many emails end up in spam folder of customer

*.pl addresses - all seem to fail after about 3 days with something like:
"abcabc[AT SIGN]o2.pl:
193.17.41.45 does not like recipient.
Remote host said: 450 Please try later
Giving up on 193.17.41.45.
I'm not going to try again; this message has been in the queue too long.
"

I need someone to get this all working properly for me

Thanks,
Roy