Hello, I have a problem as shown in the attached print screen. I have many other mailboxes in Thunderbird and I don't have such problems with them. The one that is causing the error is an old mailbox with a lot of old emails, so it probably needs some memory. Have you encountered this issue before and how did you solve it? Since the message is in Polish, below I paste the translation: "Saving the message in the mailbox failed. Please check if you have the necessary write permissions in the system and if there is enough free space available to copy the mailbox." Please help me. Regards, Kamil Borkowski