Hello
I am a system and network administrator, with more than 10 years of experience.
During that period I have installed, administrate and maintain a large number of various servers, such as Web Server (Apache, IIS), Mail Server (Postfix, Exim, MS Exchange),
DNS Server (BIND, Unbound, MS DNS), etc., based on, FreeBSD, CentOS, RHEL, etc. And of course, I have a lot of experience working with MS Servers and other MS products.
As well as I have some experience in the database design, development, and maintenance.
As for the project, I'd like to highlight that Mailgun, and other tools like that (e.g. Mandrill, SendGrid, Amazon SES, etc) are simplifying mail sending procedure, providing reports, logs, delivery information, and a lot more, but they won't affect the reputation of your Domain/IP it it's poor or somewhere blacklisted. Even more, Mailgun itself can block your email from being sent, because of poor reputation. However, it will provide email verification API, suggestions on how to configure your DNS records, and so on.
Thank you in advance. Looking forward to hearing from you soon.
Sincerely
Eduard