Conditionally pre-approved is marketing mumbo jumbo for "you still may be declined". But the good news is that you probably have a better than fair chance (how's that for my own credit talk mumbo jumbo?!)
The condition is that your credit report will be pulled again (this time as a hard inquiry of credit)
Your name appeared on the mailing list because you met a preset credit report "advertiser inquiry". This is good.
Remember inquiries only go against your credit score if you have numerous in a given time period of the "hard inquiry" variety.