Steve on 16 May, 2018 08:50 AM
thanks for taking the time to report this problem and providing screenshots to allow us to better understand the issue you are seeing.
Your key is fine. You extended the subkey and you are all good and ready to use your OpenPGP key.
You write "having this problem for a long time that was due to an expired subkey. Now I am having the problem again." I assume you are referring to the invalid signature you see for your posts to a yahoo group?
The invalid signature is a separate issue and completely unrelated to the expired subkey which you already solved.
As mentioned in our reply from 25th Jan 2018 some group / mailing list software "successfully" manages to destroy valid signature when processing the messages.
You can attach both the sent and the received message as .eml file and we can check if there is a workaround to prevent this:
Please export the message you sent from your sent folder as well as the received message with the invalid signature, so that we can have a closer look. To export, simply select the message in Mail.app and press CMD + SHIFT + S, select "Raw Message Source" as type and save it.
Attach the resulting .eml file to this discussion by visiting it in your browser (email reply should work but sometimes attachments do not arrive).