I send individual welcome letters to each new PSA from my personal email account. I do this because I feel it shows that I am willing to go outside the business framework to communicate with my team, that I'm available even if I'm not logged into SFI.
I also do this because group mailings feel like group mailings. I am open to having a personal relationship with members of my team. This lets them know that they are more than just part of the group.