Error: unspecifief

Same here. Unspecified pops up every time. How to fix that?

This e-mail must be checked (for this purpose it is necessary to manually create at least one letter with the return address of the web interface, then click “send confirmation” and follow the link from the letter)

So do I need to login to your website. Go to my account and confirm an email somehow there?

Yes. You should go in your account and create new campaign, using selected list

SZ141008-01 [Subscription error: reply address for invitation messages not set in list ‘5456242’]

Let’s try this:
1. Go to contact list – https://cp.unisender.com/en/v5/contact/subscriber/list/%LIST_ID%
2. Select in left bar “Opt-in and opt-out tools”
3. Fill data for confirmation email.

perfect! thank you!