I often get

unrouteable mail domain "<here, the domain name is listed>"

error messages. What does this mean in detail?

Regards,
Oliver

Hello,

I found out something regarding the unroutable domain problem:

if someone has capital letters in their email address, I'll get this error. Here is an example:

John.Doe@nobody.com would fail
john.doe@nobody.com will work

shouldn't it be possible that the mail engine will handle this issue?

Regards,
Oliver