What is the most reliable and fastest way to transfer zip-files?

What is the most reliable and fastest way to transfer zip-files to my customers? Yesterday, when I've finished a translation job and were about to submit a zip-package on 2,33 MB (the maximum is almost always under 25 MB so these zip-packages are quite small) for some reason I was not allowed to upload it at my usual e-mail client for attaching to the message (web hosting provider Just Host). Today, this same file worked fine without problems to upload as attachment to my e-mail message though.

Also, yesterday I uploaded this zip-package at Google Docs (which has been the best way so far to submit files to customers). But my Spanish customer couldn't access the zip-package this time for some reason.

So I'm considering two other alternatives:

1. Upload at my own website by using DocMan. Would this be any difference to what I've done so far (upload at Google Docs or send as attachment to an e-mail message from my webmail provider JustHost)? In what way would it be different?

2. Send as via ftp. I'm not certain though how to do this (think I would need to use Putty or something). Would this be something worth considering? Or is there any other protocol that would be better to use?

Would even an encrypted torrent be possible? At a legitimate torrent site (if they exist)? But that sounds like the same as Google Docs. Or change file type, from zip-file to something else that is easier/faster to transfer or upload? Doesn't my questions here, basically, depend on two things: file type and type of server I upload at (plus my own computer)? What is the optimum constellation what regards file type, server and own system configuration for reliable and fast file transfer?

An extreme solution would be my own intranet connection and my own server and upload there. I'm planning to later purchase a combined server/laptop but the price tag is rather high so I will wait for a while. Intranet connection is as expensive as this server/laptop. But in the end, would this be the optimal solution, the absolute best solution for reliable and fast transfer of files to customers anywhere in the world?

Or use another operative system or language (Linux, DOS etc.) and use some software specifically for transfer files?

This is extremely important for me because I'm exhausted after having translated for several days, and in that condition, when the actual transfer of finished job doesn't work, trying to find out what's wrong is not very easy.

Something also that needs to be taken into consideration is the fact that my internet connection sometimes can be rather slow (although it's quite acceptable now when I have my own connection here in mainland China).