Solved How to diagnose an inbound undeliverable without access to the headers?

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Solved How to diagnose an inbound undeliverable without access to the headers?

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Hi All,

First post here.

I'm moving a lot of my domains over to MailPlus Server on a DS918+ within a Windows AD domain and I'm seeing an issue where some inbound emails are not delivered. The problem is that I don't have enough information from the Audit log to see what is different about those failed emails. They mostly come from bulk mailers with emails that I have subscribed to. I have an account selected as the catch-all but they don't get delivered to it either, so I'm scratching my head on how to fix this. The Audit log just says 'Failed'.

All the emails from the multiple domains are forwarded to a single domain with a unique username to identify which domain they were sent to. Mostly this works fine, but there's just this one main problem that's bugging me. I've tried white-listing the sender domains in both MailPlus Client for the user and in the Server Security settings and it doesn't make a lot of difference.

That sounds like a good approach - I'll give it a go when I get a bit of spare time - thanks.
OK - I've just turned SPF off as it's a quick and easy change - just wait and see what happens over the weekend now...
Turning off SPF & DKIM has allowed one of the mailshots through, but not the others, which are still "Failed". I've turned off DNSBL for now to see if that sorts out the rest, but I'll probably end with more unwanted than wanted getting through...
If that’s the case then it could be that the emails started going through a stricter screening process now with the move to Synology’s mail.

I’m surprised that white-listing them is not making any difference!
You can raise a support request if you don’t mind Synology logging into your NAS, because most likely they’ll ask for that.
Over the last couple of days I've done a few things, including unsubscribing or changing the email address for a subscription where that is allowed. I've also changed the way I receive the emails on some of the domains. I was forwarding them to an address on the main domain that identified the original domain - i.e. to [email protected] was forwarded to [email protected] where was the primary domain in MailPlus. I've now removed most of these forwards and instead pointed the MX records for the other domains to the MailPlus external address. So far things are looking better, but there's definitely a lot of places where whitelisting can be specified within the server and knowing how they are prioritised would be useful. Guaranteed though, after making the latest changes there's less coming in to prove the system! :cautious:
Just had a few of the problem mailings arrived and they all got through successfully. So it looks like the forwarding was causing the problem rather than any specific filtering or blocking. :rolleyes:

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