Hello,
On a new Blesta install I kept getting a warning while setting up the Department mail accounts that the PECL mailparse was not installed. However, it was installed and functioning correctly. The true issue was that phpinfo was disabled and Blesta could not verify that mailparse was loaded. I spent a good amount of time troubleshooting mailparse when it was actually the disabled phpinfo module. This may be an edge case, but it would be more helpful for the system to recognize its verification method could fail via phpinfo and not that the required modules aren't installed.