@Osiris - Thanks for confirming. That’s what I thought. After running one of the online SSL/TLS testing tools and it reported that the Root was ‘missing’ and flagged it red it got me headed down this path in thinking that perhaps it would be better if the server presented the full chain. I also saw @swisshuttles having a similar issue and his site was only presenting a portion of the chain as well. iOS Mail not trusted?
That SSL/TLS testing tool was:
https://www.sslchecker.com/sslchecker