There are two basic approaches you could consider.
The first approach is to use events. I do not necessarily recommend this approach since most people like some experience under their belts before tackling events. You can write a routine and tell Outlook to execute it every time a particular event occurs. For example, there are the send email event and the email received event. You could write a routine that is executed every time you send an email. I would not do too much in that routine since you do not want to slow down your normal work. You could perhaps add the time and receiver email address to the end of a text file. A similar routine could record the time and sender email address when an email is received.
Another routine could be run once a day to process these text files. I would write this routine in Excel VBA so results could be written to worksheets which would help you develop your macros. This macro would have to match emails sent to John Doe against emails received from John Doe and produce a list of emails to which you have not received reply. The receivers of those emails are the people to whom you want to send a chaser email.
If the above approach appeals to you, split it into its components. Do not search for a routine that does everything you want because you will not find it. Do not post a question asking for the routine to be written for you because this site is for programmers to help one another develop; it is not a free coding site.
Look up Outlook events. I do not think the help on Outlook VBA is as good as the help on Excel VBA but it is there. Find examples of the two event routines you require. Look up text files. How do you append to a text file? It is not difficult. How are you going to match entries in the sent and received text files? Perhaps the easiest starting point is to copy the file contents to worksheets which you then sort by email address. Code your macros one step at a time. If you have difficulty with a particular step, come here for help. There is no restriction on the number of questions you can ask providing each shows the code you have tried and explains what is not working as you want/expect.
The second approach is a routine that searches Inbox and Sent Items once a day and extract the information recorded by the event routines. I have already given you a link to a routine that searches Inbox and outputs selected properties of each email to a workbook. This could be the skeleton of the routine you need.
You could search the text bodies of emails you receive for strings of the form: “[CR][LF][CR][LF]On Fri, 4 Nov 2016 at 13:43 zzzz > wrote:[CR][LF][CR][LF]”. Almost all replies to your emails will contain text in this format where zzzz will be your name and xxxx@yyyy will be your email address. This could help matching.
I have tried to give you some ideas. I doubt you can achieve a 100% perfect match between sent and received emails but if you work slowly through the necessary steps you could create a very helpful set of macros.