Hi Gagan,
I’m also a Postmark user and a WordPress developer. I was very happy to discover your updated version of the PostMark plugin and I would like to offer to help with maintaining it.
I already fixed some minor issues here: https://gist.github.com/guillaumemolter/1ce281d1fa9d5f7ccb30
Let me know if you are interested.
https://www.ads-software.com/plugins/postmarkapp-email-integrator/
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