Tags on IMAP accounts depends on tag support from the server.

If the server says it supports them and is actually misconfigured then your tags will disappear. If it says it supports them and does then they will be stored on the server. If it says it does not support them then your tags will be stored locally only.

So basically without doing all the checks (which only you can do) I would guess your mail server is misconfigured by the serve administrator.

Hi Matt, Thanks for your reply. I guess it is something like this but how can i check that myself? My web mail server can show some Tags but they are different than the one from Thunderbird.

My computer skills are limited... Do you know any company that i can hire to help me to solve this problem?

Thank again for your help. Nicolas

Just an update : I made a video to show the problem of the tags that doesn't stay : https://youtu.be/OR-_QkTI4Z4 I tried in the safe mode but i doesn't change anything : https://youtu.be/WsouLRokDNU

Anyone can help me? :)

Anyone can help me? :)

I update again hoping some help one day :)

you keep bumping this thread. What exactly do you think you are going to get, other than my ire at being emailed everytime you do it.

You can add tags to local folders and see them stay, or you can get into technical logging. I suggest you do not as you say your skills are limited, just accept they do not work with your server.