Error - no matching private/secret key found to decrypt message

[Leberkasus Semmelus]

)Hello,
this problem seems to be quite old, I tried to find a solution here in the forum but got more and more confused...
I have windows 7, thunderbird 60.6.1, Enigmail 2.0.10 and installed gpg4win using the Enigmail assistant.
When I send encrypted and signed emails to myself, they are decrypted without any problem.
When I send encrypted and signed emails to my contacts, they can decrypt them.
When my contacts send me encrypted and signed Emails, I get the error message as shown in the subject.

I looked at the Enigmail log and tried to find the messages mentioned here: https://www.enigmail.net/index.php/en/faq?view=topic&id=14#faqLink_2, but couldn't find anything.
Any idea on how it can be solved?

Don't know if it is relevant, but if I email Adele wth my public key as an attachment, the answer states "However, I could not
find a public key that matches your email address so I cannot
reply with encrypted messg". Could this be linked?

Thanks!

EDIT: added a logfile.

[Patrick Brunschwig]

This means that your correspondent did not encrypt the message with your public key. You don't have the secret key to decrypt the message, and therfore you will never be able to decrypt the message.

You need to send your correspondent your public key, and ask them to use the key you sent them instead of the one they currently use.

[Leberkasus Semmelus]

Ok, thank you for the quick answer, I will do that!