Recently, a small academic society I belong to lost the person who had been looking after member contact details. There was backup copy of the full member list but we now have to rebuild the mailing list based on this. We did not use a properly managed mailing list system: Here I will report systems that other academic groups use:

This might be one of the best open source and free systems:

"GNU Mailman -- the world's most popular mailing-list manager -- has been in constant revision for two decades and supports more than 20 languages.

MailmanLists hosts group mailing-lists -- using GNU Mailman -- on servers around the world, and provides customer support 24 hours a day, 7 days a week." (Mailman website, 2nd Sept. 2022)

https://www.mailmanlists.net/

The University College London (UCL) uses Mailman and gives advice on how set up a list and manage it:

https://www.ucl.ac.uk/isd/how-to/how-to-use-mailman