Yes, you can include some personalized
information in bulk mail

We all know that Marketing Mail bulk mail can't include personalized information, right?
Wrong!

But sometimes, you can also include additional information like the amount of a previous donation, or a subscription expiration date, and still use send the letter as Marketing Mail bulk mail.
You can include personalized information if:



The personalized information must have no purpose other than supporting the solicitation.
For example, you can include the amount of a previous donation in a letter asking for another donation. But, if you also use the letter as a tax receipt for the previous donation, that's a second purpose unrelated to the solicitation, and it forces the letter to need to go First Class.
Here's a graphic to help explain this:

Here's the relevant USPS rule, along with several related USPS rulings:
Rule 243.2.2, Domestic Mail Manual: Contents for Marketing Mail -- Personal Information
Ruling PS-322: Donation Solicitation/Previous Donation Receipt
Ruling PS-238: Renewal Notices
Ruling PS-323: Computer-Prepared Mail Pieces Entered by Authorized Nonprofit Mailers