henningw left a comment (kamailio/kamailio#4336)
As I know "urn" cannot contain `@` char. Here is [RFC link](https://www.rfc-editor.org/rfc/rfc5031.html#page-5)
service-URN = "URN:service:" service service = top-level *("." sub-service) top-level = let-dig [ *25let-dig-hyp let-dig ] sub-service = let-dig [ *let-dig-hyp let-dig ] let-dig-hyp = let-dig / "-" let-dig = ALPHA / DIGIT ALPHA = %x41-5A / %x61-7A ; A-Z / a-z DIGIT = %x30-39 ; 0-9
As I understanding allowed letters, digits and "-" char only.
Yes, but this is the standard for the URN service namespace, not the generic URN standard.