Those symbols on Pen Friends list indicate the communication status with your friends.
- Envelope w/ Yellow Arrow: Your friend is sending you a letter.
- New!: You have received a new, unread letter from your friend.
- Yellow Dot: You've read the new letter and your friend is waiting for your reply.
- Envelope w/ Blue Arrow: You are sending your friend a letter.
- Return arrow w/ Date: You have replied the letter, with the last status update time of the conversation.