Beginning Sunday, January 27, it will cost more to mail first class letters, postcards and packages within the US. The cost to mail a first class letter will be 46 cents, while the cost to mail a postcard will be 33 cents, an increase of 1 cent for each; this is the third increase for postcard postage in less than two years. This month, the USPS will also introduce a First Class Mail Global Forever Stamp that will allow customers to mail 1-ounce letters anywhere in the world for one set price of $1.10. The cost to mail flat-rate Priority Mail packages and letters will also increase. Click here for more information on all the postal increases.