that should suit your interests. Look in `.env.production.sample` to see which SMTP variables you need to set.
Note: just adding the Mailgun add-on is not enough. You will need to verify Mailgun, at which point you can use the sandbox domain _IF_ you verify individual email addresses to send to, but if you want this to work with arbitrary email addresses, you will need to add and verify your own domain, which will require DNS changes. Adding your own domain also generates a new postmaster adddress and password, so complete this before editing config variables for best results.
If you deploy from the web, the format for all the S3 bits use Paperclip conventions:
S3 Bucket is just the name of the bucket, e.g. `bucketname` not the full ARN.
S3 Region is the AWS code for the region e.g. `ap-northeast-1` not the name of the city displayed on the AWS Dashboard.
To protect the privacy of the users of the your instance, you should have permissons on the your S3 bucket set to no-read and no-write for the public and non-application-specific AWS users, with only one authorized IAM user or group set up to be able to upload or display content. This is an example of an IAM policy used for the S3 bucket used Mastadon instance hentai.loan: