Problem with Exim and message_size_limit

[Avatat]

Hi guys!
I have little problem with Exim (version 4.85).
In /etc/exim.conf, size limit of message is set to 20 MB:

message_size_limit = 20M

I have tried to send simple message with one attachment which size is 18,3 MB (19 292 160 bytes in Windows) but I have got error like "message size is the big". It isn't possible to text and headers take over 1,5 MB size..

What can I do with it?

 

[zEitEr]

Hello,

Due to how email attachments are encoded you can actually send only 10Mb in total if you have a limit of 20M in exim.
So if you need to send attachments of size 20Mb in total you should set message_size_limit to 40M.

 

[Avatat]

Thanks for your reply Alex
But.. I tried to send email with 13,2 MB (13*910*016 bytes) attachment and everything was fine (limit was set to 20M). Could you explain this?

 

[zEitEr]

You can read this: http://ask-leo.com/why_are_emailed_attachments_larger_than_the_original_file.html

It's said there:

The actual growth depends on several factors, but is mostly related to the encoding scheme used.

and this:

You're not sending the original file, you're sending an encoded version of it that can be anywhere from 20% to 60% larger than the original file. It doesn't matter what size you see on the disk. The size of the transmission will always be larger.

from here: http://answers.microsoft.com/en-us/...ent-size/74d123de-33ee-4791-bd65-63d9c455b16a

and this:

There is no encoding defined which is explicitly designed for sending arbitrary binary data through SMTP transports with the 8BITMIME extension. Thus, if BINARYMIME isn't supported, base64 or quoted-printable (with their associated inefficiency) are sometimes still useful.

from http://en.wikipedia.org/wiki/MIME

So the final size might be 20% to 60% bigger than your actual attachments and it depends on your mail program and scheme it uses to encode email.

 

[Avatat]

Thank you very much!
Now I understand everything

Have a nice day!