I was using my account normally all day, sending and receiving emails. Suddenly, this afternoon, emails are not coming through. I realized this because I setup an alias and wanted to test it. When that email didn't come, I tried my primary address, and still cannot receive the messages. I have tried sending from both iCloud and Gmail accounts and neither of these external messages are received. I did try sending to myself from within my account, and that one came into the inbox. My outgoing emails are also working. I did not make any changes to nameservers or any of those settings.

Any tips on fixing this? When I do fix it, will I be able to retrieve the emails that didn't show up during this time?