e.email Connection refused: IPV6 address for SMTP server does not listen on 587?

Real issue for several e.email users: https://community.e.foundation/t/since-lately-i-couldnt-use-deltachat-no-more-with-my-e-account/21163/

analysis: the e.email smtp server has one IPV6 and one IPV4 address. IPV6 delivers connection refused while IPV4 works:

$ host mail.ecloud.global 
mail.ecloud.global has address 135.181.85.105
mail.ecloud.global has IPv6 address 2a01:4f9:c010:c4fd::1

$ telnet 2a01:4f9:c010:c4fd::1 587
Trying 2a01:4f9:c010:c4fd::1...
telnet: Unable to connect to remote host: Connection refused

$ telnet 135.181.85.105 587
Connected to 135.181.85.105.

"e.email" probably shouldn't advertise an IPV6 address if it doesn't accept connections on the smtp-port it advertises in its autoconfig settings https://autoconfig.e.email/mail/config-v1.1.xml