Just FYI:I hit the same error with my mailserver running Debian's courier-mta: icedove could suddenly no longer send mail using SMTP+STARTTLS. Turns out the (Debian) default for the generated Courier DH key is 768 bits.
I filed #787579 to change this default.
Regards, -- Mourad DC -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org