It could be useful to collect statistical information about the use of public keys.
This information could be presented if the user needs to make decisions about keys.

Details that we could remember, per {correspondent's email address, key fingerprint}:

• first time this key was seen/advertised/downloaded as being associated to that address
• first time we used this key for encrypting email to this address, or that we saw a valid signed email from this address using this key
• the most recent time we used it for the above
• how many times we used it for one of the above

I find this is a very great idea.

Not sure if this is the right bug for this.

This is my own real life user experience:

TB 78.10.0

• Exchange keys with mail communication partner
• Exchange encrypted and signed mails successfully
• Receive an encrypted and signed mail from communication partner again
• Answer on the mail: Answer is encrypted automatically
• Then you think "Hey I forgot something" after some minutes and compose a new mail to communication partner "P.S. ..."
• The composed mail is sent unencrypted

It is not understandable to the user, that encryption is not automatically enabled when composing a mail to a communication partner with whom you successfully and recently exchanged encrypted mails.