How to send messages on VKontakte and not be blocked?

Question

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A few months ago, I created a page where the user could log in through the social network and thereby leave a piece of information about himself in the form of the page address and name, which he was warned about on the main page. I won’t say that I really collected a lot of addresses, but it’s normal and basically these are VKontakte pages. After half a year, they will have to be somehow notified of the results of the work and, since the registration has already actually taken place, to inform that a second one is not required and to remind the address. That is, no personal information needs to be transferred, just notify these users in any way and, most importantly, do not fall under the SS block. How to check it?
ps If you did something wrong, you can correct it, there is a maximum of six months.

Answer 1

You can safely write on behalf of the community. But for this you need:
1) users themselves are the first to write to the community
2) Allow the community to write through the widget https://vk.com/dev/AllowMessagesFromCommunity