CAUTION: ORACLE CLOUD >> Outbound SMTP PORT 25 is blocked

We have spent hours to find out what happen to not receiving any emails recently. So quiet so good, there is no happy new year greeting mail from ourselves. Hold on, it doesn’t make sense. Yes, we have found the SMTP port 25 is blocked, totally blocked, confirmed by oracle cloud : Outbound SMTP is blocked.


Outbound SMTP is blocked

Services: Networking, Release Date: June 24, 2021
Tenancies made after June 23, 2021 are by default not allowed to send e-mail via outbound TCP port 25 to the internet. Tenancies made prior to June 23, 2021 are unaffected. If you require the ability to send email from your tenancy, open a service limits request to request an exemption.

Impossible to fix it by yourself

Oracle cloud Security List: The setting allow all outbound traffic.

You may try to fix it like your router/gateway. NO, this is not the way you think it is. There are 3 layers or more firewalls on each gateway. Only the 2 viewable firewalls you can change or modify it, the rest is oracle maintain/control. Simply to network structure below:

Your Machine/instance
Your security list or Network security groups (NSGs)
(Networking > Virtual Cloud Networks > vcn-######)
Oracle Cloud Global Firewall


Options are limited, we have tried the following, let’s see which one is not crossed.

Service Limit Request

The “Request limit increase” locates at the bottom of the help/support side window.

You will find yourself need to upgrade to a paid account in order to submit a service limits request. (Not sure if you can do via live chat during your first 30 days free trial without an upgrade.)

After chooise PAYG plan, key in your information, and oracle checked (maybe), your card will be charged $100 bucks, and oracle said they will automatically transfer back. THEY SAID.

Oracle: Account upgrade request is in progress.

The paid account upgrade takes longer than expected, and it looks like they don’t wanna take your money, but your card details. (Remember how do they check your id in their big data with your tiny credit card – still in fresh memory. )

A long wait… 6 hours converted account to a paid account.


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