Clearbit Connect might be a bit more popular than ContactRescue. We know about 1 link to it since March 2021 and only 1 link to ContactRescue. We are tracking product recommendations and mentions on various public social media platforms and blogs. They can help you identify which product is more popular and what people think of it.
This is the best one I know of: https://contactrescue.evercontact.com/. Source: over 2 years ago
If you're not into LinkedIn, you can certainly email them too. Here's a cool extension: https://connect.clearbit.com/. Basically, it'll let you find any email within a specific company (e.g., a recruiter at XYZ company). Source: almost 3 years ago
Pulse Uno - Let them know about you.
ZoomInfo - ZoomInfo is a B2B database providing detailed business information on people and companies.
Amplemarket Midas - Enriched contact information for your lists of emails
LinkedIn Sales Navigator - Sales tool for LinkedIn users.
Google Contacts - Google Contacts is Google's contact management tool that is available in its free email service Gmail, as a standalone service, and as a part of Google's business-oriented suite of web apps Google Apps.
Hunter - Find all the email addresses related to a domain