> See the inflation factor of SMTP msg size versus attached file size. > >No, it's Base64 encoding that creates overhead. All email actually > >happens in ASCII... > > > >15.5*4/3 = 20.66 + headers and suchlike will bring it up to around 21, > >22 Meg. > > > >To be on the safe side, if you want 20Meg attachments then you need to > >set a message_size_limit of about 28Meg: > > > >20*4/3 > >=26.66 > >+ 1.44 meg for headers, long message, etc... indeed Base64 has an > >overhead of slightly more than 4/3, it would seem, from my experience.
Wietse's 4/3 is a much faster way of doing a more accurate calculation that I am a proponent of, but there is still one issue many seem to miss when looking at this. 1 meg is not 1,000,000 1 meg = 2^20 (two to the power of 20) = 1024 * 1024 = 1048576 So while many who want to allow a 10mb message try a message size limit of 10000000*4/3 that gets you 13333333, which is short a good deal from 1048576*4/3, or 13981013. And 4/3 is actually a bit low, so feel free to pad things a bit if you really do need a large message_size_limit. --Eric
