否则 is an alternative conjunction. It indicates that if a certain condition is not met, there will be undesirable consequences.
The alternative conjunctions (转折连接词) are function words that express contrast and differentiation.
The recommendation is usually described in the first part of a sentence. In some cases, it has the meaning "it's a good thing that...".
Possible negative consequences are described in the second part of a sentence. In other words, the second part of a sentence states what can happen if a certain condition is not met.
Thank you for notifying me. Otherwise I wouldn't have known about it