Hi everyone, I need some help regarding an IPv6 issue in KumoMTA.
I was previously using IPv6 to send emails and had some source addresses configured in sources.toml accordingly. Recently, I removed all IPv6-related entries from sources.toml and switched everything over to IPv4.
However, I’m now encountering this error when sending to qq.com:
ERROR: connect to [240d:c040:1:40::133]:25 and read initial banner: bind 217.156.55.232 for source:ip-217-156-55-232 failed: Invalid argument (os error 22) while attempting to connect to [240d:c040:1:40::133]:25 transport=[240d:c040:1:40::133]:25 proto=None
It looks like KumoMTA is still trying to connect to one of QQ’s IPv6 MX records, but it’s binding from an IPv4 source IP, which obviously fails.
Is there a way to force KumoMTA to avoid connecting to IPv6 MX records, and only use IPv4 destinations when my sources are all IPv4?
Thanks in advance for any suggestions!