No. IMO does not send a notification when you unblock someone. However, they will notice when messages and calls start going through again.
The process is slightly different depending on whether you are using an Android or an iPhone, but the general logic remains the same. Here is the easiest method. how to unblock someone on imo
: If you try to message someone you've blocked, you might see an option to unblock them directly from the conversation error message. This option isn't available in all versions but can be convenient if you attempt to initiate a conversation with someone you've blocked. how to unblock someone on imo
Unblocking does not restore previous chat history. IMO does not store messages sent while a contact was blocked. how to unblock someone on imo