"Could not create user" error in SmarterMail

Email > Webmail/SmarterMail
Due to a limitation in the way Windows operates, some usernames are not permitted in SmarterMail. These are:
con
aux
com1
com2
com3
com4
lpt1
lpt2
lpt3
prn
nul
Note that this limitation also applies to usernames with a period following the reserved word, such as; [email protected].

So, for example, these usernames will fail to be created:
[email protected]
[email protected]
And these will be created successfully:
[email protected]
[email protected]