Hello Everyone,
User does no longer receive notifications , when a ticket is assigned to him or he is cited in a comment. He received an alert his account is no longer managed.
Up to December, 2023 he were receiving normally e-mails notifications from Jira.
He’s checked “other” mailbox in Outlook and there isn’t any e-mail there, too.
"Get email updates for issue activity when: watching, reporter, assignee, mentions."
Thanks for your answer.