I'm aware of a similar defect in a different version, where the operation fails if there are too many dots in the domain portion of the address. I can't find any similar potential defect reports with respect to 10.0.1.12900-2, but I will file a report for you. I'll let you know what I find out.
In the meantime, you can create an email alias or just use the shorter domain (if that works) as a workaround.
By the way, have you tried a POST request? There was an older problem that recommended POST as a workaround.