What does this mean exactly? Is his machine a mail server?
I used to know an engineer/scientists who only used a single laptop (linux) and it acted as his mail server. When he travelled he used dyndns (or some such thing) so that delayed mail would be delivered to his laptop. Could never get a straight answer about whether this worked all the time or not (whether he ended up missing emails).
https://usesthis.com/interviews/brian.kernighan/
The screenshots are of Rob Pike's Sam editor.