ActionMailer works for Devise but not for Mailboxer

Question

My application is configured to use actionmailer to send emails. I have the smtp settings in production.rb as follows:

ActionMailer::Base.smtp_settings = {
    address: 'smtp.zoho.com',
    port: 465,
    user_name: ENV['ZOHO_USERNAME'],
    password: ENV['ZOHO_PASSWORD'],
    domain: 'example.com',
    authentication: :login,
    ssl: true,
    tls: true,
    enable_starttls_auto: true
}

Now emails from Devise (eg password confirmation, registration etc) work just fine, but emails from other gems like mailboxer and payola. Is there any other place I need to have these settings? Can someone help with how to put these settings in secrets.yml instead?