Can receive mail but can't deliver

NethServer Version: Latest

Hi guys! I would like to make a home mail server using Nethserver. What I have done is bought a domain, configured Nethserver with it, requested Let’s Encrypt Certificate, so if I go to, it uses secure http. I also created mail boxes. Now, I can configure the mail on my iPhone and Mac, they can connect to it.

If I try to send a mail from my iCloud to my personal mail server, it arrives. Even from my Gmail account but if I try to send mail from my personal email, it sends the mail as it plays the whosss sound but it won’t arrive. It doesn’t say that the mail is undelivered, nothing happens.

I also opened some ports on the router but not sure if it’s good because on the internet, I found many possibilities. So I opened 2525, 80, 993, 587, 465, 443 and 25.

For DNS, I’m not sure I have done everything good. What I have: 2xA: domain,com and mail,domain,com -> public IP
2xMX: domain,com -> "mail,domain,com
mail,domain,com -> domain,com
2xTXT: both are generated with some kind of SPF generator. (I used , instead of . in the links because I can only use 2 links as a new user)
I have seen many possibilities here as well. :smiley:

If someone can lead me to make my mail server working, I would be very grateful!
I don’t have any deep experience in networking, so please don’t blame me for “why the heck have you done this…”

I can reply only after 7-8 hours as it’s 11 p.m here and I will be available in the morning. Thank you for your understanding! :slight_smile:


Incoming mail works, so port 25 IS accessible from the internet. Gmail and others are rather fussy nowadays, about whom they send mail to. So that’s ok!

Check if your IP is “blocked” by your IP.

  1. Usually private homes / SOHO do not have Mailservers, anything sending mail must be a spamming PC, so a lot of providers put their (Client) IPs on a mail blacklist.

  2. Some providers block outgoing mail from that IP, even if reserved as a fixed IP. Some providers allow you to inform them that you’re running a mail server, and will ublock those IPs.

  3. A quick solution would be using an external (hosted?) Mailserver as a smarthost.
    At the Registrar where you reserved your domain you can usually setup some kind of services like web / mail. Setup a simple mailer, with one local account, like smtpuser. Your Nethserver can use that account to send mail from a “clean” IP, which would be accepted by most external mail servers.

  4. Spam has become a major problem for most concerned…

These links mayy help too, in verifying mail services:

Hope that helps…

My 2 cents
Andy Wismer

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Have you already take a look at this wiki?

Thank you for your reply! On MXtoolbox, I checked my IP and it’s listed as blacklisted 3 times only. Then, I will contact my ISP to unblock my IP.

I will definitely take a look at this website! Thank you for the link!

As @Andy_Wismer suggested, ISP’s often don’t allow to run your own SMTP server. Most ISP’s offer to use their SMTP instead. That’s called a ‘smarthost’.
Ask your ISP what settings (IP addres, ports) you need to make that work. When configured this way, your mailserver will use the SMTP server of your ISP as relay to send out your messages.

I contacted my ISP because to use their SMTP server, I have to be registered in there Webmail system but unfortunately, I can’t just register because in theory, we got login credentials when we ordered the service but that was more than 10-15 years ago, so I hope, they can unblock my SMTP server or they can allow me to register again.

But anyway, thank you for your help. Now, I know, the problem is not in my system! :smiley:

I can suggest another option: Install NethServer on a (small) VPS. This costs a bit of money, but running a server 24/7 costs money too (electricity + buying the server)
For as little as EUR4,- per month you already have a very decent VPS at
When running NethServer on a VPS there is no problem with sending email. I have my personal NethServer based mailserver running on a VPS already over 2 years now.

If I can’t get it working through my provider, I’m going to use VPS. In fact, this config costs nearly nothing as I got this 10 year old server (with a Pentium D) for free and fortunately, we have solar panels, so electricity not not a problem as well but VPS is still a secondary option.

Side advice… Pentium D is quite a waste of power, TDP goes from 95 to 130W, but the CPU do not bring this big performance.
Take a chance starting from MB chipset info to look for another LGA775 CPU like a Core 2 Duo: TDP lies from 65 to 75W and the performance is dramatically better.
In this example: half the power drain, but double the performance (it’s obviously only a benchmark)

Agreed on that. On my homeserver I use a Xeon D1521 processor, also with a TDP of around 75W… with a BUNDLE of power (and threads). Ideal for virtualization. Such a processor needs another motherboard and maybe other memory, so not directly an option to switch to,

Upgrading it is planned but actually I would like to replace the whole motherboard+CPU because it’s a Fujitsu Siemens D2179 board for a Primergy Econel 100 S1 and that is all I have found for CPU support… I couldn’t even found the chipset for the processor.

  • – 1 x Intel® Celeron, Pentium D or Pentium 4 processor
  • – 1 x processor slot with LGA775 socket for processors with 533 or 800 MHz Front Side Bus

I have tried a C2Q Q9400 and a C2D E8400 but didn’t boot, so stuck with the Pentium D 2.8GHz.
Before that, I’m going to buy more RAM as 2GB doesn’t seem to be enough.

Chipset is two years older than CPU i mentioned into my benchmark comparison.
Both CPUs use DDR3, your MB supports only DDR2 (Memory controller/Northbridge by itself has TDP of 10W).
So the server is for free, but it will drain a lot of power and will produce a lot of heat.
You have any place that need induced heating? :wink:

Does actually Nethserver need that much power? Like should I consider to buy a Xeon E5-2630L with 6C 12T (60W) or is it enough to get a CPU with lower TDP and doesn’t need a lots of power for just a mail-server? Or maybe I can run Nethserver as VM on my existing all-in-one server (Plex, SMB etc…)

We are far away from the topic, but i’ll try to answer.
Power is drained by hardware, and only “recent hardware” is adaptive about power consumption when idle or when at 100% occupation.
Smithfield and Presler were not able to do that, first CPUs by intel capable of adaptive power consumption on desktop and server were, Conroe, Sossaman and Dunnington.

Increasing the performance of your server (getting newer mb, cpu, faster disks or more efficient) will allow you to run more services with the same (or less) power consumption of your Pentium D/Smithfield.

Alright, I understand. Thank you for your help!

Back to my original question, I think, the problem here is the ISP blocking as robb and Andy_Wismer said. I will come back if my ISP responses and I can make my system working.
Thank you again for all of your help!!! :)))

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Continuing the VPS threadjack (and, like @robb, I’m also using Contabo and have been happy with them), a VPS is an easy way to have your reverse DNS configured properly–that’s pretty hard to do with most residential ISPs, at least in .us.

Use a smarthost to deliver email, sendgrid offer a free up to 100 emails a day, if you are sending more than that maybe worth a VPS fee.

Now, I registered for Sendgrid and set up smarthost with, port 587, registered email address + password but the sent mails still can’t be delivered. :((

Have you already verified that with a normal email client you can use the username and password for SendGrid?
Did you told to your domain that SendGrid infrastructure should send for you email and this is ok?