Att.net email only showing last two weeks of emails in inbox

I have had att.net email for 10+ years and suddenly I am only seeing the last two weeks of email in my inbox.  It is a rolling two weeks, meaning tomorrow, I will no longer see the email from today's 14th day as there will be a new 14th day tomorrow if that makes sense. This is occurring on all of my devices where I access email - iPhone, iPad, MacBook and when I log into the currently/yahoo mail page for att mail either from Safari or Google Chrome.  I've checked all the settings from every device and there doesn't seem to be anything that would be causing this to happen.  Please help me get access to not only my old emails, but also to make this rolling two weeks of inbox email go away.  I need to be able to access earlier messages.