All of my emails have disappeared from my inbox. I have a @Tiscali.co.uk email account. The last time I could see them was Thursday 16/4/20. Since then I have received new messages but everything before that date has gone. I only view my emails through the talktalk mail portal on my laptop which runs Microsoft edge. I don't use any other mobile device or third party mail utility (e.g. outlook) to view my account.
To secure your mailbox please carry out an urgent password change. Do you need help with a password change? You need to lock out anyone that's discovered your password and is downloading and deleting your mail messages.
When you do get access via the TalkTalk Mail sign in check there's no Auto forward or Filter rule diverting your mail messages.
Main Settings menu (triple line icon top right header - mobile browser desktop version)> Settings > Select the arrow by Mail in the side panel> Auto forward - disable > Filter rules - disable.
But it's possible you've archived your old mail messages. Or inadvertently deleted them. Look in the Folder view in the side panel. If you don't see the Folder view look bottom left for a double arrow icon and select that to open the Folder view. Select the arrow by Archive to open up and see year by year archives.
Also, in the case of deletion of mail messages look in the Trash folder. That's where deleted mail messages are sent.
Let me know what you see / find and if you need further help.