Mail in a box server access to port 25?

Posted on June 19, 2020

As I was following through the tutorial on the same topic (https://www.digitalocean.com/community/tutorials/how-to-run-your-own-mail-server-with-mail-in-a-box-on-ubuntu-14-04), I was successful in running the mail server droplet. However, the box has this warning:

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.

Using the command nmap -p 25 ip_address the port 25/tcp is open. I also did command ufw allow 25. And there seems to be no issue in the virtual machine firewall side. So this is more an issue with digitalocean as discussed here on another thread: https://www.digitalocean.com/community/questions/port-25-465-is-blocked-how-can-i-enable-it

But I have fellow colleagues that have established their mail servers in DO without this issue. My account is fairly new though and I am wondering if this has any factor in the DO’s policy. Has anyone recently experienced the same issue that I have? And is the only recourse using another mail provider such as Sendgrid? DO support is notoriously slow (been waiting for a reply on my ticket for over a week now). I need to definitely know that this is something that I need to migrate away from DO. Any help is much obliged.

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KFSys

July 23, 2022

Hello there,

It’s possible that port 25 is closed for external uses for new accounts. There are a few ways to go about the problem

try using ports like 465 or 587 for SMTP
use a third-party solution only for your E-mails. Good examples are SendGrid.

To expand more on blocking port 25 for new accounts, this is something DigitalOcean has been doing to reduce spam on its network. It is more that we simply cannot accurately determine who is going to send it.

Stopping spam is a constant fight, so DigitalOcean has implemented some restrictions on newer accounts. Having said that, you can always contact them and ask for the port block to be lifted on:

https://www.digitalocean.com/support/

More information here:

https://docs.digitalocean.com/support/why-is-smtp-blocked/

Hope that helps!