The first place to look is our FAQ.
If you can’t find your answer there please use the official support forum – https://wordpress.org/support/plugin/postie
If you need to supply logs to the developer please install the Support AddOn.
If you have questions about one of the AddOns please contact firstname.lastname@example.org – please note that general questions about Postie will not be answered, this is specifically for AddOn questions.
If you need some custom functionality programmed please contact email@example.com. Please be aware that the minimum charge for custom programming is US$125.