Many Unis use 'auto' emails and these can often be filtered into your junk mail.
Some schools also have excessive security filters on external emails - btw, this is one reason for not using a school email - and everything will end up in your junk mail.
You need to check your junk mail regularly to ensure that you don't miss important stuff, and in particular miss any questions that a Uni may be asking you that could delay an offer decision.
Check your junk mail regularly.