ruby mail gem ssl issues

bash

ChristopherEvans:2.1.10-alpine christopher.evans$ docker build -t 2.1.10-alpine .
Sending build context to Docker daemon 4.608 kB
Step 1 : FROM ruby:2.1.10-alpine
 ---> 5ae46ee8014a
Step 2 : RUN gem install mail
 ---> Using cache
 ---> fc1970428172
Step 3 : COPY test.rb /
 ---> Using cache
 ---> cb14a9f78b13
Step 4 : CMD /test.rb
 ---> Using cache
 ---> 7f41cf4adbbc
Successfully built 7f41cf4adbbcChristopherEvans:2.1.10-alpine christopher.evans$ docker run -it -e SMTP_DOMAIN=... -e SMTP_USERNAME=... -e SMTP_PASSWORD=... -e EMAIL_ADDRESS=... -e SMTP_CA_PATH=/etc/ssl/certs/ 2.1.10-alpine
ChristopherEvans:2.1.10-alpine christopher.evans$ docker run -it -e SMTP_DOMAIN=... -e SMTP_USERNAME=... -e SMTP_PASSWORD=... -e EMAIL_ADDRESS=...  2.1.10-alpine
/usr/local/lib/ruby/2.1.0/net/smtp.rb:586:in `connect': SSL_connect returned=1 errno=0 state=error: certificate verify failed (OpenSSL::SSL::SSLError)
	from /usr/local/lib/ruby/2.1.0/net/smtp.rb:586:in `tlsconnect'
	from /usr/local/lib/ruby/2.1.0/net/smtp.rb:563:in `do_start'
	from /usr/local/lib/ruby/2.1.0/net/smtp.rb:520:in `start'
	from /usr/local/bundle/gems/mail-2.6.4/lib/mail/network/delivery_methods/smtp.rb:113:in `deliver!'
	from /usr/local/bundle/gems/mail-2.6.4/lib/mail/message.rb:2149:in `do_delivery'
	from /usr/local/bundle/gems/mail-2.6.4/lib/mail/message.rb:239:in `deliver'
	from /usr/local/bundle/gems/mail-2.6.4/lib/mail/mail.rb:141:in `deliver'
	from /test.rb:18:in `<main>'

Dockerfile

FROM ruby:2.1.10-alpine
RUN gem install mail
COPY test.rb /
CMD ["/test.rb"]

test.rb

#!/usr/bin/env ruby
require 'mail'
Mail.defaults do 
  delivery_method :smtp, {
        address: ENV['SMTP_ADDRESS']||'smtp.sendgrid.net',
        port: 587,
        domain: ENV.fetch('SMTP_DOMAIN'),
        user_name: ENV.fetch('SMTP_USERNAME'),
        password: ENV.fetch('SMTP_PASSWORD'),
        authentication: 'plain',
        enable_starttls_auto: true,
        openssl_verify_mode: ENV['SMTP_OPENSSL_VERIFY_MODE']||'peer',
        ca_file: ENV['SMTP_CA_FILE'],
        ca_path: ENV['SMTP_CA_PATH']
    } 
  
end
Mail.deliver do
  from     ENV['EMAIL_ADDRESS']
  to       ENV['EMAIL_ADDRESS']
  subject  'Testing email'
  body     'Testing email'
end