Cannot send out mails

In my status check the following is listed:

Outbound mail (SMTP port 25) seems to be blocked by your network. You will not be able to send any mail. Many residential networks block port 25 to prevent hijacked machines from being able to send spam. A quick connection test to Google’s mail server on port 25 failed.

Is there any chance to solve this; i.e.other port number, but where to configure in the box?

Generally the solution is to ask those who run the network to unblock that port.
For example, on Linode, you first make sure that everything else (for example rDNS) is configured properly, then you create a support ticket to unblock the port (where you also confirm that your email practices conform to CAN-SPAM act)

Thank you for th e quick answer.
But I am only a simple user and I don’t know who on the way block outgoing mails.
a) my Inetrnet provider
b) my DigitalOcean Droplet with Ubuntu 18.04 (firewall allow 25 tcp)
c) MiaB

Can I change the port somewhere?

a) Internet provider is an incredibly generic term. It can mean your wireless phone provider, residential internet provider, hosting company, etc. So I’m not clear what is being asked.

b) If Digital Ocean is your hosting provider, then this is the most likely cause of problems related to ports. Note that assuming in the command line installation of MiaB the server provided confirmation of a successful installation, it is highly unlikely to be a problem related to Ubuntu 18.04.

c) MiaB is intended to provide complete auto-configuration of the server, including the server’s firewall configuration. Based on the message reported in the GUI system checks, it is unlikely that MiaB is the cause of this problem.

It is generally not recommended to make custom changes to the ports unless you are an expert and intend to maintain your own unsupported customizations of MiaB.

On new Digital Ocean accounts you must specifically request that email ports be unblocked by opening a support ticket. This has nothing to do with any firewall settings.

Here’s an improved version of your text:

I encountered a similar issue, but it worked well initially. I contacted the DigitalOcean support team via a ticket to resolve the blockage on port 25. I managed to send an email to myself and received it from my Gmail account. However, when I tried to reply from my service to Gmail, the email didn’t go through. I suspect this is because port 25 is still blocked. I’ll provide an update here if the situation changes.

Did they open your outbound port 25?
As long as your port 25 is blocked you cannot send mail. If they refuse to open it you may use a relay.

You can test this by ssh into the box and
telnet 25

It should connect if your port is open.

Connected to
Escape character is '^]'.
220 ESMTP 4fb4d7f45d1cf-57cb741e782sm9480238a12.64 - gsmtp

they havent i switch to lenode and it works but now im facing policies issues.

What type of policy issues?


This domain is listed in the Spamhaus Domain Block List (code, which may prevent recipients from receiving your mail. See

This domain is listed in the Spamhaus Domain Block List (code, which may prevent recipients from receiving your mail. and

it was working i even sent an test

a few minutes ago

Check both your A and AAAA IPs here:

Delist yourself from as many blacklists as possible. Your VPS provider is also listed as Level 3 USIPROTECT. There is nothing you can do about that (UCEPROTECT and Polspam BL-H3)

Start from

This is most important.
Do not send out test messages until you menage to delist yourself, thus things start to be more difficult.

I have created a ticket to Spamhaus Team hoping they can remove it.



@vele what is your recommendation of server for avoiding such issue:

UCEPROTECT and Polspam BL-H3

instead of Linode provider?

Nothing! They are not relevant but just depict the level of higyne in terms of spammers at Linode. Check it from time to time if any Level 2 spammers are present on your subnet.