Unable to send emails via SMTP relay

dan7

Hi all,

I’ve set up a new VPS using Hetzner cloud and have followed the instructions to install mailcow. I can use the webmail, receive emails OK etc but I’m having trouble sending emails.

I found out that Hetzner (and most hosts) block port 25 by default, so I have instead set up a Mailjet account and I’m trying to use it as an SMTP relay. Please see screenshot of how I have this set up.

When I try to run the Test from inside the mailcow UI, it fails and says that the connection timed out.
I don’t have a Hetzner firewall set up and haven’t touched anything on the server other than logging in and installing mailcow.

The login details for Mailjet are correct as I have configured it in a regular email client and can send emails with it.

Can someone give me some advice on how to fix this please?

Thanks!

esackbauer

Did configure your domains in the mailcow UI to use the sender dependent transport map ?
Seems already the test is failing, then you need to doublecheck the forum here for outgoing rules in your VPS firewall config, it was already discussed multiple times.

dan7

esackbauer

Yes, in the domain I set the transport.

I ran this command from the docs:

ss -tlpn | grep -E -w '25|80|110|143|443|465|587|993|995|4190'

and this is the result:

LISTEN 0      4096         0.0.0.0:587        0.0.0.0:*    users:(("docker-proxy",pid=1059,fd=4))   
LISTEN 0      4096         0.0.0.0:995        0.0.0.0:*    users:(("docker-proxy",pid=1936,fd=4))   
LISTEN 0      4096         0.0.0.0:993        0.0.0.0:*    users:(("docker-proxy",pid=1999,fd=4))   
LISTEN 0      4096         0.0.0.0:143        0.0.0.0:*    users:(("docker-proxy",pid=2098,fd=4))   
LISTEN 0      4096         0.0.0.0:25         0.0.0.0:*    users:(("docker-proxy",pid=1413,fd=4))   
LISTEN 0      4096         0.0.0.0:110        0.0.0.0:*    users:(("docker-proxy",pid=2137,fd=4))   
LISTEN 0      4096         0.0.0.0:80         0.0.0.0:*    users:(("docker-proxy",pid=1375,fd=4))   
LISTEN 0      4096         0.0.0.0:4190       0.0.0.0:*    users:(("docker-proxy",pid=1888,fd=4))   
LISTEN 0      4096         0.0.0.0:443        0.0.0.0:*    users:(("docker-proxy",pid=1251,fd=4))   
LISTEN 0      4096         0.0.0.0:465        0.0.0.0:*    users:(("docker-proxy",pid=1340,fd=4))   
LISTEN 0      4096            [::]:587           [::]:*    users:(("docker-proxy",pid=1117,fd=4))   
LISTEN 0      4096            [::]:995           [::]:*    users:(("docker-proxy",pid=1942,fd=4))   
LISTEN 0      4096            [::]:993           [::]:*    users:(("docker-proxy",pid=2038,fd=4))   
LISTEN 0      4096            [::]:143           [::]:*    users:(("docker-proxy",pid=2109,fd=4))   
LISTEN 0      4096            [::]:25            [::]:*    users:(("docker-proxy",pid=1420,fd=4))   
LISTEN 0      4096            [::]:110           [::]:*    users:(("docker-proxy",pid=2147,fd=4))   
LISTEN 0      4096            [::]:80            [::]:*    users:(("docker-proxy",pid=1383,fd=4))   
LISTEN 0      4096            [::]:4190          [::]:*    users:(("docker-proxy",pid=1899,fd=4))   
LISTEN 0      4096            [::]:443           [::]:*    users:(("docker-proxy",pid=1283,fd=4))   
LISTEN 0      4096            [::]:465           [::]:*    users:(("docker-proxy",pid=1351,fd=4))

If I run

telnet in-v3.mailjet.com 587

it doesn’t connect so it seems like something is blocked, but I’m not sure how to fix it despite looking through lots of different posts on this forum already. Sorry for the lack of knowledge, I’m new to server management and trying to learn.

esackbauer

See also here, you may need to add port 587:
https://docs.mailcow.email/getstarted/prerequisite-system/#important-for-hetzner-firewalls

esackbauer

dan7
The test you made is for incoming rules, and only shows which ports mailcow is listening to. It says nothing about Hetzner firewall rules are working or not.

you need a rule for outgoing traffic.

dan7

esackbauer

The Hetzner docs say that all outbound traffic should be allowed as I haven’t set up a firewall.

Firewalls allow you to restrict or allow traffic based on rules. Inbound rules define the traffic that is allowed, all other inbound traffic will be dropped. All outbound traffic is allowed as long as no outbound rule is specified.

No Firewalls have been applied to your server yet.

esackbauer

Port 25 is blocked even if you have not defined any outbound rule…
Call Hetzner support. Maybe they also block 587, not only 25. Usually they open port 25 after a grace period of 30 days or so. But you need to ask them.

alexaung

I am also facing same issue on VPS using Hetzner cloud. I have an app in container and send the email. It is working at my local container. Not not working on Hetzner. I have tested with Brevo, Mailersender, Mailgun, Mailjet, zoo. All are not working except gmail. I use port 587 for all. I even contact the Hetzner support and they told me that there is no blocking from their end. How do you solve this issue?

dan7

I didn’t fix it unfortunately, I decided that running my own mailserver wasn’t for me after all of the initial problems. Mailcow seemed to work great, but the server issues put me off. I’ve started using MXRoute instead.

esackbauer

Yes, while mailcow makes it easy to set up, there are some requirements and especially topics to deal with which are not so easy, but that is the legacy and adaptions of SMTP which is one of the oldest protocols on internet.
You still need to know your ways around firewalls, protocols, routing, NAT, ports, basic understanding how an web application works and then all the issues around SMTP and avoiding spam and open relay.

[unknown] All are not working except gmail.

Have you tried contacting their support (i.e. mailgun)? Maybe you are blocked on their side, because of home address and/or burnt IP address (previous owner did spam)