Got an email with a code for 10 free packs

[lucas8181_PSN]

This is for people that stopped playing the game for several weeks. It's a way for SDS to get the player base back up, and sell those stubs as special packs are released. Most video game companies do this, it's not like this is unheard of.

[Collin_SDS_PSN]

1. The email is totally legit. Every marketing email from PlayStation is from PlayStation@playstationemail.com
2. As @lucas8181 suggested, this is targeted to certain players based on what they have or haven't done in-game. It is not random.
3. You can't "sign-up" to get this offer.
4. If you want future offers you need to make sure you have Marketing Emails checked in your PlayStation Account settings.
5. This offer campaign has nothing to do with the MLB The Show Credit Card.