Issue Related to Backing Up Thunderbird Messages. Trying to back up both my inbox messages and sent messages. Problem relates to backing up inbox messages. First, attempted to back-up (sing the save as function) to desktop (folder). Plan was One Drive would back these up from Desktop. Have 199,000 messages in inbox. Did not save all of them. Then tried to save them in smaller increments to external storage (plenty of storage available). Successful with 4 back-ups of approximated 15,000 messages in each batch. Now will not back-up the full 15,000 ....last successful was 5,000 messages. When it fails, message says "Unable to save the message. Check your file name and try again later." The file naming convention has been the same for all files and have carefully checked to make sure it is not the file naming convention. What is the problem? Does someone have a solution? Can you please help me so I can successfully back-up all my inbox messages? Once I figure out an approach want to continue backing up messages using this approach. Greatly appreciate your help!! Best, Monica