IF both MTA support ssl, the mail will be transfered encrypted. So if your MTA and the MTA of the other company speaks TLS, your clients on both sides also uses ssl for smtp/pop3/imap, the mail will transfered in an encryption tunnel.
No. This is called Transport Layer Security (TLS) because it only encrypts the direct connection from one MTA to the next. Every MTA on the route is able to read the mail since it processes mails above the transportlayer. Privacy can only be guaranteed if there is a direct connection between sending and recieving MTA (and both ca nbe trusted). This is not true for SMTP. To meet all privacy requirements encryption must take place on the application level. And for authentication over insecure networks it is necassary to have cryptographically secure identification data for every person to communicate with. This can't be done without the senders/receivers cooperation. -- Michel Messerschmidt 9messers@informatik.uni-hamburg.de http://www.michel-messerschmidt.de