A system, comprising: a delivering email system configured to: receive a request from a sender to send an email to a recipient; identify an authentication method of a sender account, wherein the authentication method has been performed to authenticate the sender to access the sender account; convert information documenting the authentication method that has been performed to authenticate the sender to access the sender account to a standard format based on a set of one or more rules that indicates a type of indicator to use for each element of the information of the authentication method, wherein the standard format is based on a lookup table, the lookup table indicating a value for each authentication method; modify one or more email headers of the email to include an indication of the authentication method, one of the email headers including the information in the standard format; generate one or more digital signatures for the email that include the one or more email headers within a scope of the one or more digital signatures; modify the email such that an email header of the email includes the one or more digital signatures; and transmit the email, including the indication of the authentication method and the one or more digital signatures, to the recipient at a receiving email system; and the receiving email system configured to: receive the email having the one or more email headers indicating the authentication method of a sender account of the email and the one or more digital signatures of the one or more email headers; determine that the one or more email headers are unaltered by validating the one or more digital signatures against a public key of the sender domain of the email; determine whether the authentication method indicated in the one or more email headers meets a criteria; and execute, in response to the authentication method failing the criteria, a security response against the email. a delivering email system configured to: receive a request from a sender to send an email to a recipient; identify an authentication method of a sender account, wherein the authentication method has been performed to authenticate the sender to access the sender account; convert information documenting the authentication method that has been performed to authenticate the sender to access the sender account to a standard format based on a set of one or more rules that indicates a type of indicator to use for each element of the information of the authentication method, wherein the standard format is based on a lookup table, the lookup table indicating a value for each authentication method; modify one or more email headers of the email to include an indication of the authentication method, one of the email headers including the information in the standard format; generate one or more digital signatures for the email that include the one or more email headers within a scope of the one or more digital signatures; modify the email such that an email header of the email includes the one or more digital signatures; and transmit the email, including the indication of the authentication method and the one or more digital signatures, to the recipient at a receiving email system; and receive a request from a sender to send an email to a recipient; identify an authentication method of a sender account, wherein the authentication method has been performed to authenticate the sender to access the sender account; convert information documenting the authentication method that has been performed to authenticate the sender to access the sender account to a standard format based on a set of one or more rules that indicates a type of indicator to use for each element of the information of the authentication method, wherein the standard format is based on a lookup table, the lookup table indicating a value for each authentication method; modify one or more email headers of the email to include an indication of the authentication method, one of the email headers including the information in the standard format; generate one or more digital signatures for the email that include the one or more email headers within a scope of the one or more digital signatures; modify the email such that an email header of the email includes the one or more digital signatures; and transmit the email, including the indication of the authentication method and the one or more digital signatures, to the recipient at a receiving email system; and the receiving email system configured to: receive the email having the one or more email headers indicating the authentication method of a sender account of the email and the one or more digital signatures of the one or more email headers; determine that the one or more email headers are unaltered by validating the one or more digital signatures against a public key of the sender domain of the email; determine whether the authentication method indicated in the one or more email headers meets a criteria; and execute, in response to the authentication method failing the criteria, a security response against the email. receive the email having the one or more email headers indicating the authentication method of a sender account of the email and the one or more digital signatures of the one or more email headers; determine that the one or more email headers are unaltered by validating the one or more digital signatures against a public key of the sender domain of the email; determine whether the authentication method indicated in the one or more email headers meets a criteria; and execute, in response to the authentication method failing the criteria, a security response against the email.