The ornamental design for a mail and key ringholder, as shown and described.
FIG. 1 is a perspective view of a mail and key ring holder showing my new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a left side elevational view thereof;
FIG. 5 is a right side elevational view thereof;
FIG. 6 is a bottom plan view thereof; and,
FIG. 7 is a top plan view thereof.
The broken line disclosure of mail items, key rings, keys, and wall fragment in FIG. 1 is for illustrative purposes only and forms no part of the claimed design.