re "ehlo" ;-) sur le port 25, j'obtiens bien : telnet mail.lipn.univ-paris13.fr 25 Trying 194.254.163.74... Connected to mail.lipn.univ-paris13.fr. Escape character is '^]'. 220 - EHLO me.com 250-mail.lipn.univ-paris13.fr 250-PIPELINING 250-SIZE 52428800 250-ETRN 250-STARTTLS 250-ENHANCEDSTATUSCODES 250-8BITMIME 250-DSN 250-SMTPUTF8 250 CHUNKING et sur le port 587, openssl est bcp plus bavard que sur le port 465 : openssl s_client -connect mail.lipn.univ-paris13.fr:587 -starttls smtp CONNECTED(00000003) depth=2 C = US, O = Internet Security Research Group, CN = ISRG Root X1 verify return:1 depth=1 C = US, O = Let's Encrypt, CN = R11 verify return:1 depth=0 CN = mail.lipn.univ-paris13.fr verify return:1 --- Certificate chain 0 s:CN = mail.lipn.univ-paris13.fr i:C = US, O = Let's Encrypt, CN = R11 1 s:C = US, O = Let's Encrypt, CN = R11 i:C = US, O = Internet Security Research Group, CN = ISRG Root X1 --- Server certificate -----BEGIN CERTIFICATE----- PS: mettre 587 en port smtp sous thunderbird ne marche pas, je viens de tester. PS2: je peux me connecter en ssh sur mail.lipn.univ-paris13.fr (donc ce n'est pas a priori un pb "personnel" de login/password, inchangés). Hope this helps...