Email send within the domain that goes to relay server

[equinox]

I always believe that an email send within the same domain will stay inside the local network. The email shouldn't go a round trip and back to the MailPlus server.

My MailPlus server is currently using Dynu relay service (store/forward). This service will hold emails when the MailPlus is offline, e.g. hardware/software upgrade, internet/power outage. The queued emails will be delivered once the MailPlus server is back online.

However, during the recent NAS memory upgrade/testing process, I found that a few notification emails were queued on Dynu relay server. I assuem that during the process, the MailPlus server wasn't able to receive emails. The notification email address is point to my local domain, e.g. [email protected].

This brings me a question, why an email send to local domain was routed to the relay server? I was expecting that the email dropped to MailPlus inbox directly. The email should never go outside of local network.

Please advice. Thanks

 

[WST16]

I ran Mail (not plus) for a few years with an SMTP relay, when I send to another mail user on the NAS it doesn’t go out of the NAS.

 

[equinox]

I ran Mail (not plus) for a few years with an SMTP relay, when I send to another mail user on the NAS it doesn’t go out of the NAS.

Did you setup a local dns server? I didn’t.

 

[Sjeph]

I am running a mail plus server currently on my NAS. My isp mails server is my SMTP relay. I do use local DNS servers, but I think the configuration of the mail server takes care that mail addresses recognized as internal addresses should not go via the SMTP relay.

 

[equinox]

I think I figured it out.

Under Control Panel->Notification->Email, I use Dynu relay server as the SMTP server. So even though the notifcation email sends to a local recipient, it is forced to router to the relay server.

I changed the SMTP server to my local server, e.g. mail.mydomain.com and it works.

Thanks

 

[WST16]

Did you setup a local dns server?

I did for a different reason. To overcome SPF check problems. This was on Mail not Mail Plus. Just in case you face the same. Easy to setup. But for now, if it works don’t fix it

Check this:

SPF failing

I have recently enabled SPF, DKIM and DMARC on my NAS running mailserver. All seemed to be working fine until I got messages from people trying to send me mail that it was bouncing. On investigation, it only when the MailServer perfoms an spfquery on an incoming message and the response is too...

www.synoforum.com

 

[equinox]

I did for a different reason. To overcome SPF check problems. This was on Mail not Mail Plus. Just in case you face the same. Easy to setup. But for now, if it works don’t fix it

Check this:

SPF failing

I have recently enabled SPF, DKIM and DMARC on my NAS running mailserver. All seemed to be working fine until I got messages from people trying to send me mail that it was bouncing. On investigation, it only when the MailServer perfoms an spfquery on an incoming message and the response is too...

www.synoforum.com

I registered my domain name on GoDaddy and setup the SPF, DKIM and DMARC there.

Another reason I don't want a DNS for my local network because I have multiple PCs, and other devices shared with families. So I don't want to rely on the NAS DNS cause I don't know how much down time for the NAS. Now the MailPlus email system is the only email system I am using, can't affort the hardware failure. I may think of buying another device as a backup. Thinking of XPenology or FreeNAS, but haven't figured out how to install an email system yet.

Setup a local DNS, you need to open port 53. That's I prefer not to.

 

[WST16]

setup the SPF, DKIM and DMARC there.

Do you mean that you've set it up in the DNS records on GoDaddy's (TXT field) or is it actually doing the (SPF) verification on their systems?
SPF verification takes place on your Mail server as far as I know and to do that you’ll need to enable it.

 

[equinox]

I created a TXT record for SPF on GoDaddy DNS manager. GoDaddy will NOT do it for you.

However, since I am using Dynu relay service, I don't know if the SPF record is still affecting me.

 

[WST16]

However, since I am using Dynu relay service

Is it for outbound and inbound mail or just outbound?
When someone send you an email, does it go to the relay service before it’s sent to you or does it come to your mail server directly (over port 25)?

 

[equinox]

SPF is for outbound. It is for email receipent to verify your emails.
Here is my SPF record on GoDaddy.

 

[WST16]

Yes I understand. But you’ll need (not a must) to do the same, verify SPF on emails arriving to your Mail server. How are you doing that?

 

[equinox]

Yes I understand. But you’ll need (not a must) to do the same, verify SPF on emails arriving to your Mail server. How are you doing that?

MailPlus has an option. It is under Security->authenticatio, there is an option of SPF.

I left it unchecked. I found that there are too many legitimate emails fell into junk folder when I enable it.

 

[WST16]

Yes, when I was running Mail, I enabled that option. The only problem I faced was having rejected emails if their SPF records were long. The DNS fix above took care of that.
You can run without it for a while and see. If you're ok and you don't have a lot of spam then keep going without it.