If you have a pop mail account on both laptop and pc. Pop mail accounts do not synchronize folders. When you download using Notebook it leaves a copy on the server. When you use the pc, as the emails have not been deleted off the server by Thunderbird on the Notebook, this means you can download them again onto the pc. when it downloads to the pc, then the copy left on the server is deleted. This means you will have a copy of the same email on both Notebook and laptop. '''Q:''' Why does NoteBook does not seem see that emails it has in its inbox have been deleted on the server? '''A:''' Because if it is a Pop mail account, it does not synchronize with the server; it just connects with the server and looks in the Inbox for new previously not downloaded emails and downloads if there are some. You are not viewing the remote Inbox, you are viewing emails stored on your Notebook. If you have Pop mail accounts on both Pc and Notebook, this means there is nothing wrong with your setup. It is working correctly. What other options do you have? You could use your notebook to access the webmail account to view emails on the server. When the pc connects, downloads and deletes, those emails will be removed from the server and so you would not see them. But you would also not have any store of emails on the Notepad. If your webmail account offers IMAP as well as Pop. Create a new IMAP mail account on the Notepad and use it to connect to the server. This means the IMAP mail account will offer a remote view of the server. If pc deletes an email, this will be shown on the server and therefore you will see this via the IMAP account on the Notebook. You can still download a copy and store it in Local Folders, these copied emails will be stored on your Notebook and are not effected by any deleting done on the server. You need to 'subscribe' to see IMAP folders held on the server. Right click on remote Inbox and select 'Subscribe', a list appears and you can select the folders. You can also synchronize folders. In this case a copy of the folder is downloaded, so you can see emails when in offline mode, but any synchronized folder will get updated by the server to reflect any changes. More on IMAP accounts here: * https://support.mozilla.org/en-US/kb/imap-synchronization