Are you using IMAP or POP with this account? Given the size of the account is so small, I would recommend POP with removal of mail from the server upon download. That way you will always have an empty inbox on the server.

POP. Yes, I have this option but wouldn't this be dangerous? It might take away a message before I have a chance to read it. Maybe this is a stupid reflection. Is there a difference between the inbox from my provider (Tele2) and what gets in my Thunderbird inbox? Two different boxes? Meaning that the moment the message is registered in Thunderbird it stays there, even if I zero my provider inbox?

Ternov said

POP.

Be very sure. almost everything being said here is invalid if you are using imap.

Yes, I have this option but wouldn't this be dangerous? It might take away a message before I have a chance to read it.

When Thunderbird gets it into in your inbox there, it deletes the message from the server. What is dangerous about that? The post office do not keep a copy of your mail after they put it in your letter box. You do not leave a copy of your letters in your letter box when you take them inside. Why should email be different.

Maybe this is a stupid reflection. Is there a difference between the inbox from my provider (Tele2) and what gets in my Thunderbird inbox? Two different boxes? Meaning that the moment the message is registered in Thunderbird it stays there, even if I zero my provider inbox?

The process with pop is (when it is set to delete massages) is that mail is essentially transferred to the Thunderbird inbox through fetching the mail and then deleting it.

Thunderbird asks the server for new mail, it replies with a list and then Thunderbird asks for each email on the list one at a time and inserts it in your inbox in Thunderbird then it sends a message to the server to delete the message now thank you. You can also set Thunderbird to delete the mail after a number of days. Say 7 or 14 so even if thing go pear shaped you have the last week or two of mail on the server.

But to answer that last question. There is no relationship between the inbox on the server and the inbox on Thunderbird when you use POP. They are synchronized when you use IMAP and are essentially the same thing one is a copy of the other and changes to one directly affect the other.

The setting I would discourage using is the leave on server until I delete it. That one has a habit of not working for some technical reasons beyond the control of Thunderbird or you and me. When it does not work your account fills up. Not what you want.