Post Offices are nowadays a service integrated in various shops; grocery stores, kiosks, gasstations etc. The opening hours therefore differ according to the specific store. Generally the opening hours are very generous. Look for the blue postal sign.
International letters and postcards of up to 20 grams cost SEK 5.50 within Sweden and SEK 10 outside Sweden.
Stamps are available for sale at Post Offices and most newsstands.
There are two different types of mailboxes. The blue box is for local deliveries only, and the yellow box for national and international deliveries.