UUCP delivered email (and Usenet and file transfers) for a very long time before full time network connections became the norm.<p><a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;UUCP" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;UUCP</a><p>So, it is possible to send&#x2F;receive email without an always on network connection.