SMIMEA

Calculate SMIMEA RFC8162 Record from S/MIME Certificate
Version 0.01.

openssl genrsa -out smime.key 2048
openssl req -new -key smime.key -out smime.csr \
  -subj "/CN=you@example.com/emailAddress=you@example.com"
openssl x509 -sha256 -req -days 365 -in smime.csr -out smime.crt \
  -CA ca.crt -CAkey ca.key \
  -setalias "Self Signed SMIME" -addtrust emailProtection \
  -addreject clientAuth -addreject serverAuth -trustout
cat smime.crt

Then copy and paste output:
-----BEGIN CERTIFICATE-----
MIIEEzCCAfsCAQEwDQYJKoZIhvcNAQELBQAwazELMAkGA1UEBhMCVVMxCzAJBgNV
....
shtN9l5XXWffVM2UuaxqVr4ULLm2z3PeGPNBzrlAWSvY+7kCuY3d
-----END CERTIFICATE-----

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