Thanks a lot for your bug report. Unfortunately, I was not able to reproduce the issue.
Can you please let me know, which e-mail provider you are using where this happens? Also let me know how the e-mail thread is structured (so which e-mails were incoming and which ones were outgoing)?
Email Structure: It was a conversation aimed at multiple people. All persons are using “Reply All”. I haven’t replied to the conversation(in any manner). I have read the entire conversation on the Browser. But Its still showing Unread in MailSpring App even after reading the same in MailSpring too.