Should I send my postcard in an envelope?

Postcards are usually mailed without an envelope. So, by default, if you're sending a postcard to another member, mail it without an envelope. Most members prefer to receive their postcards this way.

However, in some countries, postal services may require postcards to travel in envelopes, or there might be clear advantages to that method of sending them (protection from likely damage or curious eyes, etc.). Some members indicate this on their profile. If you can, try to follow the recipient's recommendations.

Keep in mind that in many countries, the postage is more expensive to send a postcard with an envelope than without it (plus the cost of the envelope). Both methods are acceptable, so it's up to you to decide how to send your postcards.