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.
Best Answer
My guideline for unknown recipients is 5MB, but I try to keep it to 1MB if possible.
In three years at my last job, we did run into at least one or two cases where a ~5MB message was rejected, and we couldn't really get enough info from the recipient to troubleshoot more. Zipping the document got it through, and that satisfied the senior executive on our end.
Remember that not all recipients will have the knowledge, the patience, and/or the ability to determine if they have a size limit (or a block on certain extensions). So the larger the message, and the more arbitrary the other user is, the more likely you are to get caught in a morass.