Unable to request an invite

[stenwt]

Describe the issue

My org uses a .co domain name; when we request an invite from the community Slack inviter, we get rejected saying the email address is invalid. I have confirmed inbound emails work.

[jberkus]

/sig contributor-experience
/area slack-management

I've confirmed that the inviter will not send to the person's otherwise valid email address. Not sure how to proceed from here.