Q: If a tzedakah organization sends me a stamped return envelope, a CD, or a sefer and I am not interested in donating, must I return the item? Can I use it?

A: Since the stamped envelope, CD or sefer was mailed to you intentionally, it is not considered an aveidah; the owner knows where it is. Even if you do not want to donate, you are not required to return the item to them. In most situations, you are even permitted to use the stamp or gift, since they sent it with the full awareness that only a percentage of people send a donation (C.M. 261:1-4; Pischei Choshen, Geneivah 1:[26]).

However, some are stringent not to use the stamp or an item of significant value (e.g., a sefer) for personal use, especially if payment is clearly expected. Nonetheless, you are not required to return it or notify the organization. If a long time passes and they do not request the item, you can make yourself a note about it, and then use it. (Hashavas Aveidah K’halachah 12:5; Tzitz Eliezer 21:50).

If mail was mistakenly delivered to you, you should give it to the addressee or return it to the sender.