Basic script for sending out bulk email via mailgun.com

I have client that wishes to send out a one time bulk e-mail to his databse of emails, consisting of around 13,650 email adressers (not a bought spam list or similar, all emails have actively signed up with client earlier). They wish to use [login to view URL], and I have set up a Mailgun account for them, changed the DNS records etc. so it should be all good to go. I need to get a script written and run. From what I beleive you can use PHP, Python, Ruby or Java (see [login to view URL]) It can be sent out in several rounds if needed. Bounce rate will probably be a bit higher than normal, but that’s OK. (Domain is 5+ years old and properly setup with GoDaddy. ) It's quite urgent, I need this done before end of the year. Thanks