Seems mailinabox give csr that not include *.domain.com in admin->ssl_certificate, so we need to do some little trick
SSL Domain example
example.com
box.example.com
So in example.com nginx ssl cert and key store in /home/user-data/ssl
you need to create new csr and key, before that please delete
so
rm -rf /home/user-data/ssl/ssl_certificate.pem
rm -rf /home/user-data/ssl/ssl_private_key.pem
rm -rf /home/user-data/ssl/example.com/ssl_certificate.pem
cd /home/user-data/ssl
openssl req -nodes -newkey rsa:2048 -keyout ssl_private_key.pem -out server.csr
and then configure your ssl with server.csr value after that comodo will give you 4 file
AddTrustExternalCARoot.crt
COMODORSAAddTrustCA.crt
COMODORSADomainValidationSecureServerCA.crt
STAR_example_com.crt
copy this 4 file into your /home/user-data/ssl, you need to concatenate this 4 file with this command.
cat STAR_example_com.crt COMODORSADomainValidationSecureServerCA.crt COMODORSAAddTrustCA.crt AddTrustExternalCARoot.crt > ssl_certificate.pem
copy also your ssl_certificate.pem to /home/user-data/ssl/example.com with command.
cp ssl_certificate.pem /home/user-data/ssl/example.com
Lastly restart your nginx.
service nginx restart
Voila Works.
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