Install the app
How to install the app on iOS

Follow along with the video below to see how to install our site as a web app on your home screen.

Note: This feature may not be available in some browsers.

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

6
2
NAS
DS918+
Operating system
  1. Linux
  2. Windows
  3. other
Mobile operating system
  1. Android
  2. iOS
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.

Grahame.
 
Hi,

An idea that I’m not too sure of.
Would it be possible to add another address to these lists you’re subscribed to? If possible, add a service that allows you to examine the headers, like ProtonMail or –God forbid– Gmail and compare it with the ones that are successful.
 
That sounds like a good approach - I'll give it a go when I get a bit of spare time - thanks.
 
Another thing you might want to try is to disable SPF checks and test for a while to see if they go through. If it’s SPF, it could be DNS related.

I suggest that you try this first as it’s easier to do.
 
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 mydomain.com 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:
 

Create an account or login to comment

You must be a member in order to leave a comment

Create account

Create an account on our community. It's easy!

Log in

Already have an account? Log in here.

Thread Tags

Tags Tags
None

Welcome to SynoForum.com!

SynoForum.com is an unofficial Synology forum for NAS owners and enthusiasts.

Registration is free, easy and fast!

Trending content in this forum

Back
Top