If you using image with direct link (for example hosted on s3) in letter, mail.ru parser will substitute it with point. Yes, regular point, like this - .
For ruby on rails + carrierwave + s3 you can use
config.fog_use_ssl_for_aws = false
in carrierwave config (config/initializers/carrierwave.rb) to get all s3 links with "http" instead "https"
