Re: [exim] Attachment sizes - confusion

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Autor: Evgeniy Berdnikov
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A: exim-users
Assumpte: Re: [exim] Attachment sizes - confusion
On Tue, Sep 08, 2015 at 06:55:27AM +0000, Osborne, Paul (paul.osborne@???) wrote:
> However I sent myself a file through to test this:
> -rw-r--r-- 1 po35 po35 24021574 Feb 15 2015 test-pdf.pdf
>
> Which is about 23MB in size and so was somewhat confused that when it got to Exim to find that I got the following message:
> message too big: size=32873715 max=26214400 (25MB)
>
> So whilst I appreciate some growth where the attachment is
> re-encoded and packaged up to be sent via email I was to be honest
> mildly surprised that there was a 25% growth in attachment size.


32873715 / 24021574 = 1.3685

Where did you find 25%? For Base64 encoding the expansion ratio is
exactly 4/3, so encoded file grows by 33% of it's original size.
And you have to add size of mail headers.

> - but it does make things a bit of a pain when I need to advertise
> a hard figure as a maximum size that we will allow through our mail
> system when that does not correlate to what the user sees as a file
> size usage on their disk.


Correlation is strict, described by a trivial mathematical formula,
but numbers are not simply equal. Users have no willings to know
encoding details, but you, if you have a job related to computing,
you have to learn some mathematical relations.
--
Eugene Berdnikov