I know that Yahoo and Google mail support 25MB email attachments. I have an idea from somewhere that 10MB email messages are generally supported by modern email systems.
So if I'm sending an email between two arbitrary users on the internet, what's the safe upper bound on message size? 1MB? 10MB? 25MB?
I know that one answer is 'don't send big emails, use some sort of drop box'. I'm looking for a guideline if you are limited to only using regular smtp email.