Answer
As specified by RFC822 a “.” may be used to separate words, this means that the final character in the username portion of an address may not be “.”.
While it was possible at one time to create an address such as this we did change it in NTMail V5 to more closely comply with the RFC.
If an address of this format is desperately needed then you can create it directly in the registry, you should note however that there would be no difference between account “xxx.yyy.” and “xxx.yyy”
Keywords:Email address, valid, 822