How to avoid email to a Group, with external recipients, going to spam

Hi,

I hope this hasn't been asked too many times before, but it's difficult to think of a tight enough search term to find existing discussions; please let me know if there is.

I have recently set up a Zoho (free) account hosting my domain's email and created a group that contain external email addresses. All the people on the group have clicked on the link they were sent to say they're happy to receive the mails. The group is set up to allow anyone to send to it, as it's a committee for a non-profit organisation and everyone needs to know what's going on.

I've been told that some of the messages sent to the group are going to spam/junk folders on, at least, hotmail accounts. I'm not sure about gmail, but that's a possibility too. I'd like to try to work round that but I'm not sure of the best way.

I've read about SPF, DKIM and DMARC, but I'm not sure if those will help. Actually, I'm pretty sure SPF won't because the emails to the group come from a variety of email addresses and are passed to the group with the "from" address intact. As I understand it, if SPF stuff is checked, it'll look at the sender's email address and check if the domain (e.g. gmail.com!) is set to allow Zoho to send email from it. I do have an SPF entry in my domain's DNS to allow Zoho to send it's mail but, as I mentioned, the mail's not coming from 'within' the domain. I haven't taken as close a look at DKIM or DMARC; would configuring those help?

Alternatively, is there another option available?

Any help or suggestions would be gratefully appreciated.

Many thanks