Tom Smyth writes:
Are there other hosts?
Many! Costs and services vary enormously, though. I choose to run my own server and MTA because dogfooding, but there are a lot of services that will manage Mailman instances for you, and you just provide the domain and list owners.
How is this not a bigger issue for Mailman users?
Not sure what "this" refers to, SMTP relays? They're a huge issue for instances that don't have other reasons to run an MTA. But if you're hosting email accounts or running MX for an organization you have a lot of other problems, and dealing with the Mailman-specific aspects basically amounts to using the DMARC mitigations, good abusive mail filtering, and implementing the ARC protocol.
Maybe most are big institutions that have their own SMTP relays and dedicated staff to keep deliverability/reputation high?
As far as I can tell, people with just a couple of discussion or non-commercial announce lists, a few dozen members at most, and low traffic, do very well with cheap services that run the MTA and the Mailman instance, and they just handle the list owner stuff. Instances that do more than that typically are serving an organization that provides hosting and SMTP relay service.
Or maybe a lot of people are using DMARC mitigation so that the 'from' address is always the list address?
For most discussion lists, there really is no alternative to "Munge From", at least for p=reject posters. "Stealth DMARC" (where large providers like Gmail require From alignment when they receive messages from themselves) is annoying, but we have an option to deal with that.
Under some circumstances it is possible to run lists that never alter the message, but those are pretty restricted because many jurisdictions require "easy unsubscribe".
-- GNU Mailman consultant (installation, migration, customization) Sirius Open Source https://www.siriusopensource.com/ Software systems consulting in Europe, North America, and Japan