A PrintableString is a restricted character string type in the ASN.1 notation. It is used to describe data that does only consist of a specific printable subset of the ASCII character set.
According to the ASN.1 Specification of basic notation, 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.
References
PrintableString Wikipedia(Text) CC BY-SA