[AusNOG] Current "Best Practice" WRT email size

[Ross Wheeler]

On Thu, 26 Nov 2015, Mark Newton wrote:

> Go back to the question, “Why does the limit exist?”
>

> SMTP servers used to have the limit because large files took a long time 
> to send, bandwidth was expensive, storage space also cost a lot of 
> money, and if a message was too big the client would probably crap its 
> dacks when it tried to receive it anyway.

SMTP is the smallest part of the problem.


> Even a decade ago, 10 Mbyte limits were the norm. You’re currently 
> happy with 16 Mbytes, even though all the resources which were extant 
> when the limits were first envisaged have scaled by, what, a factor of 
> 1000 in the right direction?

Not really "all the resources".


> You currently have a limit which prevents your users from sending a RAW 
> format image off their digital camera as a file attachment. That seems 
> unusually small to me.

I keep stats on the number of messages, message sizes, rejects etc, and 
very rarely do we see an email rejected because of size. This is the first 
call I've had about it in probably 5 years.


> Is there any specific reason why you couldn’t update it to 1 Gbyte?

My real gripe (about email size caused issues) actually stems from the 
collection side. I'm not interested in a p!ssing contest about pop vs 
imap, but for largely historical reasons the vast majority of my customers 
are using pop3. Some of them are so important they feel the need to check 
for mail every minute. These are probably the same ones with a gigabyte 
of email sitting on the server. Copying the mail drop and parsing for 
these mailboxes IS a resource hog.

I can just imagine the problems when these same people start getting 
"movies by email"... and it's suddenly 2, 5, 10GB of email. Then it'll be 
the "movie-a-day-by-email" club, and they'll want to leave them all in 
their mailbox because they "might want to watch it again"....

There are practical considerations. For the majority of my customers, 
it's never been (and unlikely to ever be) an issue.