Technical features

This page of information is certainly the least accessible of this web site. It is necessary to have a knowledge of the format of the messages transmitted by electronic mail (in particular encoding MIME) to follow all the details.


At the beginning, Internet protocols were developed for the United States of America, before being used in other countries.
This internationalization required to take into account alphabets richer than the American alphabet.
Moreover, after the basic texts, the protocols of electronic mail integrated the possibility of sending texts with page-setting and file of any nature.
Unfortunately, for each encountered problem, several distinct technical solutions were adopted, without most of the time, such a diversity had of practical interest.
In addition, the complexity of the standards makes that they are not exactly respected by the mailers, due to difficulties of application, or due to very aproximative implementation.
In practice, the majority of the mailers use a limited subset of the possible formats of messages.

Two choices are thus possible: It is the second approach which was adopted for Libremail.
However, version after version, Libremail supports more and more particular cases, without to having become much more complex than at the begining.

Processing of the received mails according to their structure

Structure of the messages sent

For the sending of mails, Libremail is only limited to two structures of message:

Encoding of the characters

As specified higher, protocols Internet initially were American before being internationalized. However, American population has 2 characteristics which distinguish them from the majority of the people of planet:
For the electronic mail, it is the 2nd point which is most important, in particular because in the beginning, Internet protocols were planned for a transmission of the characters on 7 bits.
Under these conditions the characters having the 8th significant bit (set to 1) had to be encoded.
Remainder, even today where the transmission of the characters on 8 bits spread, the standard of transmission provides that the characters of the heading of the messages having the 8th positioned significant bit will be always encoded.
Two formats of encoding exist: the format "quoted printable" and the format base64. These technical choices are appropriate perfectly in the developed countries (for example France), but are not can be adapted to other areas of the world like Africa (to be checked).
If it proved that in these countries, the accentuated characters are correctly transmitted in the fields of heading (in particular in the subject of the mail), and in the enclose files, but not in the text of the message, it would be necessary to create and use a modified version of "envmail" so that these messages are transmitted with the encoding quoted printable.

Recognized character sets

Hour and time zone

For the display of the dates and hours of forwarding of the messages, Libremail did not take account of the time zones until version 2.1.4 .

Since version 2.2, the command vmailsj corrects the variations (in full hours) between the time zone of the sender and the time zone of the recipient and account it to make a chronological sorting of emails using of different time zones.
The tools being used to visualize the contents of the emails continue to display such as they are in the sender's emails dates and hours and the time zone of the sender.