A PrintableString is a restricted character string type in the ASN.1 notation.
It is used to describe data that consists only of a specific printable subset of the ASCII character set.
According to the ASN.1 Specification of basic notation,[1] the character set of PrintableString can be expressed as: The PrintableString definition does not include the at sign (@) or ampersand (&).
This sometimes causes problems for naive implementers who attempt to put an SMTP email address into an X.509 digital certificate Distinguished Name.
The PrintableString definition does not include asterisk (*) which means it must not be used to represent a wildcard in an X.509 digital certificate Distinguished Name.