You can reach prospects who ignore your LinkedIn InMails in at least ten different ways.
I am sure you familiar with some. How many of the following methods do you use in practice? (Please feel free to comment.)
Email. If an email address is associated with a LinkedIn profile, your message will land in the same email Inbox as an InMail. However, the email comes from you, while InMail has a linkedin.com return address. Gmail users may get your InMail in the “Social” category, which they never check. Others ignore everything LinkedIn sends! Email does not have that