Hello,
My name is Dmitry. my and my team has build email platform emercury.net. it is similar to mailchimp, but focused on adveretisers.
Lets think out of box: if you will try to send 30K emails to just created addresses daily, you would burn all sending IPs in some minutes and this would be it. You need IPs, yiou need warm up process, you need recipients lists etc.
You can make your own mail server, install MTA there, but it will take much time and cost. So I would suggest to use any ESP (emercury, mailchimp, constantcontact etc) that have APIs. You will have a simple php script, that crawls classifieds and send API requests to ESP to send emails.
Yes, you will have to pay ESP for sends, but it is less than you would spend for your MTA server.
What do you think?