Friends you may never see

• Rings round newspaper proprietors at first for correspondents
• Friends you may never have met
• Friends who may never meet
• Letter-exchanging friends
• Exotic stamp collectors, maybe
• Friends by mail
• Writing set?
• "84 Charing Cross Road" correspondents, e.g
• Foreign correspondents, perhaps

Wiktionary Word definitions in Wiktionary
n. (plural of penpal English)