There is currently an issue with the Webmail interface at https://webmail.webfaction.com which is resulting in sporadic 500 Internal Server Errors for some email users. We are looking into the problem and hope to have normal service restored soon. We will update this entry as soon as we have more information.
2018-03-27 11:25 UTC: The problem has been solved. If you see any other errors, please feel free to contact our support team by opening a ticket.