@JTJames,

yes it's a long-standing bug, see post #2 here: https://community.tp-link.com/en/business/forum/topic/175422

I reported this bug already for Omada Controller v2.5 back in 2018. All mail providers I know of use STARTTLS even on port 25. Only Omada Controller doesn't allow to use TLS on arbitrary ports, but insists of using port 465 for encrypted mails which is deprecated since more than 20 years now.

Nothing changed since the bug reports except that you cannot set port 587 anymore at all in SDN Controller. I have no idea why Omada Controller lets you define a port if it then dictates what port to be used instead.

What's more, EHLO SMTP greeting message is broken, too.

Reported already in 2017: https://community.tp-link.com/en/business/forum/topic/100931?replyId=218390

Reported again in 2020 here: https://community.tp-link.com/en/business/forum/topic/217556?replyId=465610

Dear @JTJames,

I've an issue with the new Controller Version: 4.1.5. Within the Mail Server setting, port is everytime automatically changed to 465 no matter what I configure (target is port 587).

 

Confirmed with the R&D, this is a display issue, the port is actually set to the target port after you save the settings and see the response message "success", but just not showing correctly on the page. The developer will fix this in the later new version. Thank you again for your valued feedback!

Fae wrote

Confirmed with the R&D, this is a display issue, the port is actually set to the target port after you save the settings and see the response message "success", but just not showing correctly on the page.

Dear @Fae,

I can't second that.

Just did a quick test: I enabled »SSL« setting and set port to 25 overriding the default port 465 (yes, we use SSL on port 25). This is the input before applying:

Next, I applied the settings, got the »Success« message and was immediately been logged out from the web UI (why logged out? No idea).

After logging in again, I tried to send an email. According to the developer, the target port 25 now should have been set no matter what is displayed, right? Then I should be able to send an email. To find out whether this really happens, I monitored TCP/IP traffic of Omada Controller on the gateway using tcpdump.

But first here are the mail settings displayed in Omada Controller:

Now I did send the test mail. As you can see from tcpdump protocol, Omada Controller (IP 192.168.1.46 in our LAN, DNS name oc200.mydomain.lan) established a connection to our SMTP server, but still tried to connect to port 465 (service name: ssmtp) to deliver the mail, not to port 25:

I already did report this bug so many times now for so many versions of Omada Controller (it's still present in V2.5, V2.7, V3.x and V4.1.5, together with the EHLO bug).