I’m not sure but I think the only one we have had these problems is relay.mailchannel
I think I have addressed it before for one or two years ago
And our host Interserver support gave me advise not to use Capital Letters in emails it was one of five items to follow . Mailchannel which had same info. I don’t have it in front of me now but at the time I made changes in ubb language editor but it came back with 7.7.5 as I forgot to keep my language files.

I will look into your suggestions and and see if I can make it better but please listen to the Capital Case suggestion as it’s not me but the trade who say one should not use it.
With that info
I think It would be better if the opposite was default.
Cheers