On Thu, Jun 28, 2001 at 06:36:59AM +0000, John Seago wrote:

Can anyone tell me why my messages to ALUG have =20 at what I presume is the end of each line please?

I would also like to know if they appear on all my messages and how to stop it happening.

This is actually quite an interesting question, and the reason is mostly due to the fact that internet mail has been around for a long time and is designed to work despite the strange behaviour of some legacy computer systems.

First of all I guess that the mail program you are using to compose your messages allows you to type without having to worry about the ends of lines - the program wraps the lines for you at a word boundary.

The mail program wraps the lines of a paragraph by trying to start a new line between pairs of words. Normally between two words there would be a space character and your mail program doesn't remove the space characters at the points where it splits the paragraph into lines, so when the paragraph has been split into lines, all but the last line will have a space character at the end of the line.

Now we come to those legacy computer systems. Most modern operating systems store text (which a simple mail message is) in files with variable length records (lines) and use a delimiter (newline, aka. LF for Unix/Linux, CR+LF for DOS/Windows, and CR for Macintosh) to separate one line from the next. Some older operating systems store text in fixed length records and "pad" the lines out with spaces on the right hand side to make them all the same length.

On it's way through the internet a mail message may get stored temporarily on one of these old systems that uses fixed length records and if that happens it will have to be converted to fixed length records by padding out the lines with spaces. When the next hop is a system with variable length records then the lines have to be converted back. To convert from fixed length records into variable length ones we take each line and remove all the spaces at the end of the line, and insert the line delimiter (newline etc.) at that point. If this was to happen to your mail message which started out with the spaces at the ends of the lines then those spaces would be lost.

To protect your mail message from having the spaces chopped out, your mail program protects the message by using a "Transfer-Encoding", in particular the transfer encoding called "quoted-printable". When applying this encoding, characters that are in danger of being lost or misinterpreted on the way get converted instead to a three character sequence, the equals sign followed by the character's numeric code in hexadecimal. The code for a space in 20 in hexadecimal so =20 represents a space character. Of course, now the equals sign is used for something special if we wanted to send a real equals sign we have to encode that too and that then becomes =3d.

Your mail program declares the fact that it has used a transfer encoding by adding an extra header line to the message. From the header of your original message (the one to which I am replying):

X-Mailer: KMail [version 1.2] MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable

What is supposed to happen is that when someone's mail program recieves your message it will notice that a transfer encoding has been used and will reverse that encoding before presenting the message to the person reading it, so the =20 sequences at the ends of the lines would be converted back into single spaces. Where this doesn't happen (and the =20 gets displayed instead) it suggests that the mail program reading the message is too old to understand about transfer encodings, or else just doesn't decode them correctly anyway.

So finally, what do you do about it? If you want to be sure that no-one sees your messages with the =20 at the end even if his or her mail program is old or broken then you can make sure you keep the lines down to less that about 70 characters rather than have your mail program wrap them for you. That way the spaces at the ends of the lines won't be there to start with. Alternatively you can take the view that if other people's mail software is old or broken that isn't your problem.

Hope this Helps Steve.