Limit memory usage when mass-sending emails
In a large course with a large exam, keeping all emails in RAM like we do here may take several gigabytes of RAM.
To improve on that I propose to collect all data except for the PDFs, and attach the PDF when sending the message, rather than before.
Original description
The feature "Email to everyone" failed several times for the exam https://wbmt1051_2022.grading.quantumtinkerer.tudelft.nl/exams/6.
Individual emailing works, but with 500+ students that is not really time-efficient.
Could you please try to fix this quickly?
Edited by Anton Akhmerov