I understand the importance of attachments.
But it's the only way to make email hosting cheap or free, bc attachments occupy 99,9% of disk space.
But anyone who tries to auto-delete my attachments will never get my patronage.
Why do you want to cripple email to create a free service? This seems like a race to the bottom, with very little upside for you.
Limiting attachments - the only possible way for free ADs-based alternative.
Mail search - will be offered. But old emails w/o attachments.