Around 0300PST, Amazon Web Services reported an issue with increased error rates in a queue that we use (Amazon Simple Queue Service - N. Virginia) which caused emails to be stuck in processing.
AWS reported the problem resolved around 3 hours. After this time our team manually pushed through any emails still stuck, and have made repairs to the system so for future outages, emails will automatically be processed after resolution.
You can follow Mailparser's status here and on the AWS dashboard, as well as the RSS for the queue we use: