Well, you could just not look in your sent box and you won't see them again. Beyond that, not sure. Sent box doesn't exist as such in v3, all messages are threaded, so it is unlikely that the problem will be fixed on v2.
How to permanently delete my messages?

I have folowed all that...but whn you click on SENT ITEMS you can see you messages there...
That is the problem...i wanna remove them forever... There is an option to delete them in that section...but they are again there,,,strange,,i'll talk with staff

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That is the problem...i wanna remove them forever... There is an option to delete them in that section...but they are again there,,,strange,,i'll talk with staff
If it is a bug then it is unlikely to be fixed since programming efforts are on v3 and v2 will be going away at some point.

how do you delete all your messages on the new chess.com?
Click the X in the upper-right corner of the message.

Hello, there is no x mark in the upper right corner of the message to delete the message, please help
Sound a little stupid but i can't delete my 6 months old messages.
Option says ''Items in your sent box are kept for 3 months and are then deleted".
But, i am deleting them and they are always there...is there some way to delete all and you can't see them anymore?