Jakarta Mail does not resolve hostname properly when the hostname has both ipv4 and ipv6 addresses to it.

[sriram241294]

I'm having an application which runs in a docker environment. The application supports both ipv4 and ipv6 hosts. All of our services inside the container runs with the JVM option -Djava.net.preferIPv6Addresses=true preferring IPV6 addresses over IPV4.

We are trying to connect to a Office 365 SMTP server which resolves to both IPV4 and IPV6 addresses. Our host is pure v4 and when trying to send emails via jakarta.mail it is failing to connect to the host and fails to send emails. I'm observing that it is resolving the host to IPV6 address since my service specifies to prefer IPV6 address but does not fallback to IPV4 when connection to IPV6 address fails which is the idea of having -Djava.net.preferIPv6Addresses=true.

Can someone please confirm if this is the expected behavior with jakarta.mail when we try to resolve hostnames which has both V4 and V6 addresses to it?

[jbescos]

Following this here: eclipse-ee4j/angus-mail#186 (comment)