We have been using MS Exchange Online Protection for the last 8 years. It's been working good with our on-premise Exchange server.
Price we pay is 18.99$ per user per year. We are almost at 50 users.

@JasGot Awesome, thanks for the input. I'll look into SPF.

@EddieJennings I know, it makes no sense to me to disable it but I understand the reasoning behind it.

Hey all,
I have recently migrated from Exchange 2010 to 2016 and am wondering about NDRs. I see the suggested way of doing things nowadays is to disable NDRs on Exchange, to avoid BackScatters. Am I right?
My issue is how do you let legit senders know their email did not reach us? Per example, emails over the allowed size limit. Senders think our recipients are ignoring them as no NDR is being sent and we are missing important jobs that way.
Everything I search about NDR and 2016 is about disabling it.

How do you proceed with that?
Thanks!

@scottalanmiller that works for me. Sent them a reply, hopefully I didn't land on a relentless guy!
Thanks for the input, it's great.

@pchiodo This is good info, thank you. I have been plagued with yearly SAM audits for as long as I have been working for this company. I've never received requests for SAM audits before starting working for this company 7 years ago. We are 100% compliant on all licenses we need, and yet they are now asking me to prove the purchases of each 57 computers we currently have in circulation basing their request on all the free Windows 10 upgrades and not having licenses for them. When last year we passed this audit. So I think I am going to send them a note saying I will not complete this Audit.

Thanks for posting this.

@scottalanmiller Thank you! I had a different tag, was eskimo-on-fire on that one.

Hi, I just saw this and thought I would introduce myself. My name is Natacha and I am the System Admin for a company in a small town just outside of Calgary Alberta, Canada. I've been in IT for over 20 years. I was using Spiceworks quite a bit 7 years ago and somehow missed this whole MangoLasssi move. I always wondered where people went! I did find out about it while reading an old post about WSUS on SW, it came up so here I am!
So far I think this looks like a better fit, so thank you for creating this. I watched the video on how it came to be and now it makes sense.