Estonian national postal service is provided by Omniva who has post offices all over Estonia.
Post offices are open on weekdays and some on Saturdays, with greatly varying opening hours. (You can find all the information on the opening hours and also postal codes on www.omniva.ee.)
Estonian mailboxes are orange. You’ll see them outside post offices, in shopping centres and at most gas stations. To send mail, just drop your letters and postcards in the official mailbox.
Pickup times are noted on each box. Most letters take between 1-3 days to arrive within the Baltic and Nordic countries. If you send mail far overseas, the arrival can take up to a week. Stamps are sold at post offices, kiosks and most grocery stores.
Mail is delivered daily from Monday to Saturday, except on holidays.