Let’s try to solve the problem without installing additional packages on the host. Let’s try to do it with containers!
Alpine Linux has a fetchmail package: Alpine Linux packages
To start with an Howto also ns8-scratchpad + an “Alpine with fetchmail and cron” container could be enough for a PoC.
Further resources:
- Run any service on NS8
- 24 Nov 2023 - NethServer 8 Deep Dive: how to run generic containers
- The Imapsync app could be a solid base too
ns8-imapsync/build-images.sh at main · NethServer/ns8-imapsync · GitHub