I am assuming you own these database that you are talking about OP as it is illegal on BHW to talk about spamming.
1) Get a server based in Romania, Russia (the best whenever they have disagreement with USA), China, Poland, Bulgaria.
2) Setup SMTP on this server. Purpose of this server is to clean your data. Depending upon the volume of data that require cleaning, you may or may not need a dedicated server. You just need a single IP for this as the purpose is to identify hard bounces. Setup a different domain for data cleaning purposes.
3) Send a simple message saying that you have are replying to the database recipient. Remember no inclusion of links here. And do provide a subscribe option.
4) Wait for 5 - 7 days for the sending to complete and bounce report processed. Depending upon your server, this period of time can be lengthen or shorten.
5) Extract the emails that are not hard bounce (if you want to be safe, remove the soft bounces as well).
6) You would have a cleaned list on hand at this stage
7) Next set up a dedicated server using a singe domain.
8) Then install a mailing software like interspire on to this dedicated server
9) Go to your domain DNS and setup multiple sub domains. Example, aa1.abc.com, aa2.abc.com.
10) Use these sub domain to purchase VPS or Gmail business.Setup these DNS to point to their servers. You would have multiple SMTP at this stage. You need at least 30 SMTP if your database is more than 50k emails and you want to complete the sending within two days.
11) Next purchase around 5k yahoo, 1k gmail, 1k AOL, 5k hotmail/ outlook accounts.
12) Do a trial sending without link to these dummies account to warm up your IP addresses.
13) Engage a VA to manually log in to these email accounts to whitelist your your email. Remember to get your VA to switch IP for each account. Ideally whitelisting using the same country IP address of your database. Example, USA database, you should use USA IP. It does not matter if you use server IP or residential IP at this stage since anti spam system do not take this into account.
14) You only need to do this once to build up your sender IP address but you have to do for all the SMTP that you own.
15) Setup interspire stage: Send hourly limit for each SMTP to be around 300 emails max. Do not try to send beyond 300 emails. The reason is because if there are still hard bounces at this stage it will damage your sender IP address reputation. You need a few months to increase this limit as ISP get to know your IP address and domain. Next setup bounce processing and feedback loop so that your system will automatically remove spam complaints.
16) Remember to check your domain for blacklist using mxtoolbox about 4 days after you send a campaign as it take sometime for ISP to blacklist your domain/ sender IP. If there are any blacklist, you need to request for removal or simply add more SMTP through increasing your sub domain. Then remove this blacklisted IP and don't use them.
17) In all your emails campaign, always remember to include your unsubcribe option.
18) Nurture your IP addresses and the more you send with less complaints and bounces, the better reputation the IP will attain thus increasing your ability to send larger amount of emails volume.
Remarks: I usually use a sending Company service wsince it is so cheap as I can't be bother with the above steps as it take too much of my time to manage the SMTP and maintain IP address reputation. But remember, you must clean your data even if they are double opt in as bounces can seriously damage your inbox rate. Hope the above information and steps will be helpful to you. Remember don't spam and use emailing for legitimate purposes.