'Re-downloading messages and excluding existing messages' 

Thats because when you opened it using the phone, you probably used pop which downloads to your phone and then deletes the original on the server. So when Thunderbird connects with server, it cannot download something that is not there. If this is a gmail account, then they tend to only permit one pop download. You would need to alter server settings to get around it. Options: If pop mail accounts are used then make sure you have chosen the option to 'leave messages on server'. '''Re: If using gmail and POP on two different devices.''' Please read all of the information as it suggests you try two processes. One is for regular use and the other is a suggestion if you need to get emails older than 30 days to force a download. I would suggest this should be used when in general use: Gmail users can use either POP 'normal mode' or 'recent mode' to sync their mail. If you're syncing your mail to one mail client, you should use normal mode. If you're syncing mail to a few different mail clients, then you should use recent mode. Regardless of which behavior you select, any downloaded message will be marked internally as 'popped' and will not be downloaded again. * https://support.google.com/a/answer/6089246?hl=en This sounds like once you have used POP on phone, the email is marked as popped by gmail and then cannot be downloaded again to Thunderbird. But gmail have a sort of workaround called 'recent mode'. Recent mode fetches the last 30 days of mail, regardless of whether it's been sent to another POP client already. Info here: * https://support.google.com/mail/answer/47948 This should get at least the last 30 days and work better for you as you access mail via two pop devices. However, if you have many emails that are older than 30 days and you really need them on TB, then look at this info, which you could run to get all the pop emails again and then swap back to the 'recent mode' as explained above. gmail says: Once a message has been 'popped' to your mail client from Gmail, you won't be able to re-download it to any mail client in the future. Senario: for instance, you have to remove and reinstall your mail client from scratch, you won't be able to download previously 'popped' messages unless you select the Enable POP for all mail (even mail that's already been downloaded) This info is located here: * https://support.google.com/a/answer/6089246?hl=en under this heading: 'Re-downloading messages and excluding existing messages' you need to scroll down to bottom of page to see it.

Hi Thanks for the information. But I have checked my phone settings and it using IMAP so I don't understand why the messages will not appear on my pc