Reverse DNS Error and Unable to set up email on any Email Client

Hello all,

I was hoping I could get some help here on two issues I have. First,
I have seen similar post about the reverse DNS error but mine is a little bit different. The error I am getting on System Status Checks is the following:

“Your box’s reverse DNS is currently (IPv4) and [Not Set] (IPv6), but it should be Your ISP or cloud provider will have instructions on setting up reverse DNS for your box.”

Based on this message…my reverse DNS is correct but not sure why I am getting the error.

Second, I am unable to set up my email account on any email client. I have tried Thunderbird and Android Gmail. It states that the username and password is incorrect which is not the case as I am able to login through my webmail login page at

I am able to send and receive email so far and I am currently using an Ubuntu 22.04 box under Vultr.

Any thoughts anyone?

Thanks in advance


What does “dig -x <mail-in-a-box_ip_address>” show?



This is what I am getting:

; <<>> DiG 9.18.12-0ubuntu0.22.04.2-Ubuntu <<>> -x <mail-in-a-box_ip_address>
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 49979
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

; EDNS: version: 0, flags:; udp: 1232
;<dns_ip_address> IN PTR

<dns_ip_address> 254 IN PTR

;; Query time: 0 msec
;; WHEN: Tue Aug 15 07:58:20 MDT 2023
;; MSG SIZE rcvd: 117

<dns_ip_address> IN PTR this should be your public IP address in reverse order, is that correct?

That is correct. I also just confirmed that using this tool Reverse IP Lookup - MxToolbox

Well if your domain DNS is setup correctly I’m at a loss I’m afraid, hopefully somebody else can help with this.

With regards logging in with a client (I use Thunderbird without any issues) I use IMAP and my settings include:
Port: 993
Connection Security: SSL/TLS
Authentication Method: Normal Password

Outgoing Settings
Port 465
Authentication Method: Normal Password
Connection Security: SSL/TLS

are all the necessary ports available on your firewall?

Thanks for your input @gezza, yeah, hopefully someone else can help here on this reverse DNS issue (if it’s actually an issue).

Now, in regards to the email client…yes, I am using those IMAP settings. Regarding the Firewall… not sure…but you mean in my email client machine or my MiaB server?

OK never mind. That was the reason, I had to adjust firewall on my Box server. Thanks a bunch for your help! @gezza

No problem…glad that side is sorted

You have not set rDNS for IPv6.