Newsletter issues with imported members

I’m self hosting Ghost on Digital Ocean.
I have imported members from a CSV file and set them as newsletter subscribers.
In Mailgun status of emails is delivered. I don’t get any error in Ghost.

But, I tried to import test emails and newsletter is not delivered. Also, open rate stats are not displayed in Ghost dashboard.

Howevers, seems if you subscribe manually on the website - email newsletter is delivered.

Also, in Mailgun dashboard I can see that user open emails - but these stats are not reflected in Ghost.