I cannot transfer SMTP traffic in my tunnel. I had already sent emails, but did not receive a ticket number.
My local internet provider does not offer IPv6 in 2023. I run my own mail server and therefore rely on SMTP in the HE-Net tunnel.
Of course I am IPv6 Sage.
I tested again. No traffic over tcp port 25 possible. Never got an answer to my mails to: ipv6@he.net or info@he.net.
I had the same problem. For some reason, SMTP doesn't seem to work within the tunnel going to their email servers (even though your logs will tell you it does). Thus my email to ipv6@he.net never was seen, since my SMTP server was using the tunnel to deliver the message. I had to use an outside email provider to get them the email to enable SMTP over the tunnel.
Try contacting them from outside the tunnel using a 3rd party email or maybe (I never tried this) disable your tunnel while the email is sent so it's forced to use IPv4 to mail.he.net. Once I figured that out, they were actually very fast to respond. Then you can go into your tunnel settings and enable SMTP. After that you will be able to use SMTP over IPv6 but still not to HE.net for some reason...