Which free service allows customers to keep their mail at the post office while on vacation?

The appropriate service for customers who want to manage their mail while on vacation is indeed the "Hold" service. This service allows customers to request that their mail be retained at the post office during their absence, ensuring that their inbox remains untouched and secure while they are away.

By utilizing this option, customers can avoid mail accumulation at their home, which can be a security risk or simply an annoyance to deal with upon return. Upon their return from vacation, customers can easily retrieve the accumulated mail at their convenience. This customer-friendly feature helps maintain organization and provides peace of mind, ensuring that important mail does not go unnoticed.

The other options do not apply as effectively. For instance, "Deferment" typically refers to postponing payments or obligations rather than mail services. "Vacation Mail Service" sounds similar but is not an officially recognized term in postal services. "Mail Suspension," while it might suggest a temporary halt, does not align with the standard terminology used by postal services for holding mail. Thus, the term "Hold" accurately reflects the procedure and service provided for customers wishing to have their mail safely managed while they are on vacation.