Metagate on Orange webmail

Hello, try a system restore to a date and time before your problem

system restore

click on start
click on all programs
click on accessories
click on system tools
click on system restore
in the window that opens check restore my computer to an earlier time
click on next
click on a bold date or time in the calendar
choose a date or time: before the problems
click on it
click on next and in the window that opens check at the top left if the date and time match what you chose
click on next wait for the restart once restarted in the restore window telling you that your computer has been restored to date, time, and name
click on OK
check if it works, and remember to update your security tools
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Personally, I may not know much, but if the little I know can help, then I’m happy to share it with you!!

Thank you Jacques for your response,
I performed 2 system restorations (to ensure I was at a date prior to the issue). No restoration was made, so no changes have been made to my PC since 30/12.
I updated the antivirus (Symantec).
Also updated malwarebytes and did a quick scan: nothing.
However, for the past 15 minutes, I no longer have this METAGATE page appearing in front of my email. Has Orange changed something? To be continued...

In any case, thank you for your intervention.

Théo