If you have an issue, I suggest to post a new topic on the plugin’s Support Forum on WordPress.org: this is the preferred way, since very often users experiencing the same problem can share their informations and lead to a faster solution. I recommend to search in the forum before posting, chances are someone has already asked the same or a similar question.
If the support forum isn’t the right choice for you, or if you want to ask something in private, feel free to send me an e-mail using the following form.
Please use this form only for questions/messages about Duplicate Post. This is not for issues with WordPress and/or other plugins.