'You have sent a message in a trashed conversation...'
To resolve this issue, try these tips:
- You may be replying to a message that's part of a previously deleted conversation. Note that when you click the Delete button, it moves an entire conversation (not just a single message) to the trash. If this is the case, you can move the conversation out of Trash. Alternatively, it's possible to delete just one message.
- Please make sure you haven't created any filters with the action Delete it that might affect the messages in question. If you have many filters or have complicated filters in place, you may need to edit the Delete it action to guarantee that they aren't at fault.
- If you've enabled forwarding in your account, ensure that you haven't selected delete Gmail's copy in your forwarding options.
- If you're using a POP client to access Gmail, ensure that you haven't selected delete Gmail's copy in step 2 of your POP download options.
- If you're accessing your Gmail from multiple POP clients (with recent mode), verify that you've selected Leave a copy of messages on server in your client configuration settings.