If you did not install or modifiy anything and this happened all by itself, you may have a "Mail Brick"
Det1re's Mailbox Brick Fix.
Originally Posted by Det1re
If that fails, reinstall ios70 with patches and then system menu 4.2. Install with dop-ios-mod v11.5 or offline with wadmanager.
Ipsa scientia potestas est.
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Thank you all ! i will try the mail brick first & then i will follow Pobs instructions.
Yes it was the mail brick ! fixed !! thank you all for your help.