This article explains why certain links do not work as expected when inserted via our browser extension and/or URL block.
If you are getting an error when using the Letterhead browser extension or URL block, or an empty block, please test the link in https://www.opengraph.xyz. If the site cannot be crawled by websites like opengraph, it's a limitation on the side of the site that blocks Letterhead from grabbing the information. Letterhead will only be able to pull information from sites that allow for this.
Testing your desired sites or links with OpenGraph is a simple yet powerful way to determine the issues you encounter while using browser extensions or URL block.
Please ensure that the following IPs are whitelisted and our crawler's domain is safe-listed:
Whitelist IPs: 198.199.66.189 | 164.90.252.240 | 167.172.156.41
Safelist Domain: *.tryletterhead.com | letterhead.email | letterhead.ai
By whitelisting the above IPs and safe-listing the mentioned domains, you enable our crawlers to efficiently access and retrieve content from our RSS feeds.
In addition to this, the Letterhead crawler is labeled "LetterheadCurationBot", and its User-agent is below:
- Mozilla/5.0 (compatible; LetterheadCurationBot/1.0; +http://tryletterhead.com/bots)