Why haven’t email attachment file size limits increased over the years?
In: Technology
Email is not a file transfer protocol.
Email by design allows for unsolicited messages to be delivered, so if you allow attachments of any size a hacker could very quickly overload your server and fill up it’s hard drives by sending emails with multiple recipients and large attachments.
For example if I can email a 5gb ISO, It would only take a couple of emails for me to crash your server.
Email attachment size limits have increased over the years but it’s rare to see larger than 20mb for the above stated reasons.
One big problem with email is that, if a message has multiple recipients, the entire mail message is duplicated for every recipient. If some company has 1000 employees and someone emails out a 5MB PDF to all employees, then the mail server will need 5GB of space for all those emails.
In addition, the protocols that handle email inboxes means that you have to download the whole of waiting email. You can’t easily pick and choose what to download. If you send someone an overly large attachment, it can prevent them from accessing their inbox at all (This is even a problem for webmail systems which have to handle all the processing of these files, which can cause server-wide problems)
The answer is that it has a little bit…
Exchange 2003 has 10mb limit, then Gmail comes along and it’s 25mb.
The problem is that “email” is not a unified standard – there are so many different providers and email systems that backwards compatability is very important. If I email from my work email address (which is on Exchange 2010) to my personal Gmail account, and then forward it to your personal address which is running off a SendMail email server – they all have to agree.
Because of this everyone has their own arbitrary standards that have kind of stuck. There is no reason why Gmail couldn’t decide ‘max attachment size 40mb’ other than Hotmail/Yahoo/AOL don’t support larger than 10mb and you’re creating yourself a problem.
Take Exchange 2016, you can configure for your org within your org that the limit is 20mb. Or 22mb. But this doesn’t work when emailing people outside your org, so you leave it at 10mb because this plays well with others and that is far more important than trying to make Email a file storage system.
> One big problem with email is that, if a message has multiple recipients, the entire mail message is duplicated for every recipient.
This for instance has not been true for a while.
> In addition, the protocols that handle email inboxes means that you have to download the whole of waiting email.
This is probably not true, but may depend on what email client you are using. If you have Outlook Express running POP3 then yes it’s true, but it’s not 2003 anymore so it’s probably not true.
The protocols we use for e-mails really haven’t changed since the early days of the internet, with a few add-ons like encryption. In order to make sending large attachments more feasible, you would need to fundamentally change how the e-mail system works to make it more efficient for transferring large files, and every e-mail provider and client would have to adopt this new protocol.
E-mail was never meant for file transfer, we already have other protocols which are much better for doing that. In the old days, someone who wanted to distribute a file to a bunch of people by e-mail may have sent a link to an FTP site. Today, you might send a link to a dropbox location, or a Microsoft Teams session.
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