message vs attachment size

Kevin Miller Kevin_Miller at
Thu Mar 9 15:59:20 GMT 2006

Julian Field wrote:

> It's very simple, the message size is the size of the file containing
> the body of the text, for MTA's that have 2 files per message
> (sendmail and Exim). For MTA's that have 1 file per message (Postfix
> and ZMailer) it is simply the size of the file representing the
> entire message including headers and envelope data.
> Yes, I know that makes the figure slightly different for different
> MTA's with the same mesage. But people only ever use it as an
> approximate figure, e.g. 10MB. No-one cares if it is 10MB + 100 bytes
> or 10MB - 100 bytes.

Just to elaborate a bit, it may also be worth noting that when an
attachment is encoded there is about a 25% increase in filesize so if
someone asks what your limit is and you say 10 MB, from a practical
standpoint they may only be able to attach a 7.5 MB doc.  Of course,
anybody sending 7.5 - 10 MB files should be fed to the sharks, but
that's a different rant...

Kevin Miller                Registered Linux User No: 307357
CBJ MIS Dept.               Network Systems Admin., Mail Admin.
155 South Seward Street     ph: (907) 586-0242
Juneau, Alaska 99801        fax: (907 586-4500

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