Iris does not track its users, but the email servers that you choose to connect to might do so. No data about your use of the application is being collected at any time. The optional autoconfiguration feature will send the domain part of your email address to the Mozilla Foundation.
When trying to debug a problem, you may be asked to provide Iris logs. The logs do not contain email bodies, but they do contain metadata (email headers) that may contain personally identifiable information regarding the sender and recipients of an email. Providing logs is entirely at the discretion of users and requires them to be manually transmitted to the software author. Any logs provided via email will be deleted once the problem has been resolved but may be subject to retention by the email hosting service.