LinkedIn allows and encourages you to send messages to your connections on birthdays or work anniversaries. This appears as a shared post, a reply to an InMail message, or a requested recommendation. LinkedIn will also provide you with a default message for each instance.
Sending someone a generic message is like handing someone a birthday card that simply reads, “Happy Birthday.” The recipient is unlikely to feel recognized and important.
Instead, you need to think of contacting your connections in a way that makes them feel appreciated. All you need is a few seconds to change the impersonal default message to a personal one that actually means something!