That resolves to a single IP address for me (46.16.61.50) and the server there has a certificate for srv.cat and *.srv.cat, not for anything blockchainers. That’s why you are getting the error. On SMTP connection, the banner identifies the machine as fnsib-smtp07.srv.cat, but DNS lookups of that name don’t return that IP address (although it does return six others near by).
(BTW, I checked the cert with https://ssl-tools.net/mailservers in case other people want to test their servers.)
I think you need to get the *.srv.cat name for that mail server.