today heads of the majority of the enterprises and the organisations all over the world prefer e-mail (e-mail) as to correspondence means. except extraordinary high speed (the letter in any point of the world reaches within 1-5 minutes), data transmission by means of e-mail has also other powerful advantages: reliability, absence of loss of quality and low cost. by e-mail it is possible to hand over any information presented in electronic form without distortion: texts, images, sounds etc. besides, the electronic letter can be never lost. in case of impossibility of its delivery (the address of the addressee is incorrectly specified) the letter will be returned the sender within several minutes.