AuthUser=contact@mydomain.fr
AuthPass=mypassword
mailhub=auth.smtp.1and1.fr:465
rewriteDomain=mydomain.fr
UseTLS=YES

vmonteco:contact@mydomain.fr:auth.smtp.1and1.fr:465

$ echo test | mail -v -s "Test" mymail@hotmail.fr
mail: Loading /etc/mail.rc
mail: No such file to load: /home/vmonteco/.mailrc
mail: Setting up PseudoRandomNumberGenerator: *SSL RAND_*
[<-] 220 kundenserver.de (mreue105) Nemesis ESMTP Service ready
[->] EHLO localhost.localdomain
[<-] 250 SIZE 69920427
[->] AUTH LOGIN
[<-] 334 VXNlcm5hbWU6
[->] Y29udGFjdEB2b250ZWNvLm5pbmph
[<-] 334 UGFzc3dvcmQ6
[<-] 535 Authentication credentials invalid
sendmail: Authorization failed (535 Authentication credentials invalid)