Getting Large Files to People

From Daily Data

Sometimes, we get calls about "I get a message when I try to send an e-mail saying my file is too large." This is caused by limits placed on the mail servers, to keep the amount of traffic lower, and to not waste transfer.

Sending files, especially large files, can be something of a problem, and the way you do it is dependent on the size of the file, the expertise of the sender, and the expertise of the recipient.

email and MIME Encoding

Main Use: Small photographs, word processing documents, faxes, especially from or to non-technical users

• Advantages:
  • Extreme ease of use for both the sender and the recipient
  • Sender and recipient only need basic e-mail skills
• Disadvantages:
  • Size of attachments increase by approximately 150%
  • "filling up" of mail boxes
  • Slowing of e-mail transmission and receipt
  • May be rejected by the server on the sender, recipient, or anyplace in between

E-mail was not set up for pictures, programs, zip files, and other so called Binary Files. E-mail was, and is still, designed to transfer text; the basic things you can enter into a text editor like kate (under Linux), Text Editor (Mac OSX) and Notepad (Windows). However, once everyone started using email in the 90's, it became useful to be able to send WordPerfect documents, pictures and the like with an e-mail. This problem had already been solved through the use of the attachments we all use so often.

A problem arose, however. Email is not designed for these binary files (a binary file is anything other than a text file). So, something called MIME encoding was created. Without going into detail, it converts a binary file into a text file. On the receiving end, your e-mail program reconverts it to a binary file when you download the attachement.

This is a very useful function, and is very easy for both the sender and the recipient. The problems arise in that the process that makes the conversion increases the size of the file, by 8/5ths, if I remember correctly. I generally just say it is 150%. So, sending a 1 Megabyte file through e-mail increases the size to 1.5 Megabytes in your outbox, for the transmission, and in the inbox of the recipient. Because of this, all e-mail servers limit the size of attachments, with the default being 10 Megabytes for most of them. Note that this means your attachment must be smaller than 7 Megabytes (converting to MIME increases that to about 10 Megabytes). Note: the size limit is per message, so attaching 20 pictures that are a half megabyte (512 Kilobytes) to a single e-mail would easily exceed a 10 Megabyte limit.

File Transfer Protocol (FTP)

Main Use: Medium to large (extremely large) files from and to technically trained users.

• Advantages:
  • Virtually unlimited file size
  • Automatic conversion for text files to different operating systems
  • Extremely efficient transfers
• Disadvantages:
  • Requires some technical skills not necessarily a part of the average computer user
  • Requires special programs
  • Security may be a consideration
  • You must have access to a server capable of FTP

Web Based (HTTP)

Main Use: Medium to large (extremely large) files from technically trained users, but to recipients of any level

• Advantages:
  • Virtually unlimited file size
  • Efficient transfers
• Disadvantages:
  • Requires FTP or SSH skills by the sender, and the appropriate programs
  • Security may be a consideration
  • You must have access to a web (http) server