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Blocked email ports

ooogggle
Newbie
Posts: 3
Registered: ‎10-11-2021

Blocked email ports

My Email provider has recently migrated services to new servers resulting in an IP address change. Now I cannot connect to them via my Plusnet broadband any more. I can connect fine if i start a vpn to bypass plusnet filtering. So know the ports are open.

 

Using nmap i can see ports are just not open when connecting direct via plusnet. Ports blocked are 465 and 993. Email provider is mail.defencegateway.mod.uk.

 

How can i get plusnet to stop blocking these ports?

10 REPLIES 10
GlobalSteve
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Registered: ‎10-11-2021

Re: Blocked email ports

There are a lot of issues today regarding email, so it may be prudent to keep on eye on the Plusnet Tech Team info here

https://community.plus.net/t5/Service-Information/Plusnet-email-login/m-p/1837590 

 

Thanks for the port information though as that could help.  I did just change my ports to the aternatives settings but the email still doesnt work, so it may be a red herring.

Baldrick1
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Re: Blocked email ports

@ooogggle 

I suspect that there are a few red herrings here.

My guess is that it is the new IP address that is not being resolved by the Plusnet DNS which is causing your problems. Have you tried setting a different pair of resolvers in your computer IPv4 settings?

You are not using the Plusnet email server so that is irrelevant.

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GlobalSteve
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Re: Blocked email ports

Hmmm, good idea.   I will look into that soon as I can.  On my PC I have manually preset DNS server addresses so if Plusnet have changed those my DNS server may not have resolved the cache, but my mobile . . .not sure.  Bit busy this morning so may not be for a while.  

ooogggle
Newbie
Posts: 3
Registered: ‎10-11-2021

Re: Blocked email ports

DNS resolves to the same IP whether on the VPN or not. So dont think its DNS issues.

 

 

Baldrick1
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Re: Blocked email ports

@GlobalSteve 

Plusnet do not change the IPv4 DNS resolvers. Settings should either point at your preferred resolver IP addresses or the Hub IP address, where it will be redirected to one of the Plusnet resolvers.

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Baldrick1
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Re: Blocked email ports


@ooogggle wrote:

DNS resolves to the same IP whether on the VPN or not. So dont think its DNS issues.


Yes it will resolve to the same IP address PROVIDING the address is held in the chosen DNS resolver database.

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GlobalSteve
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Re: Blocked email ports

@ooogggle and @Baldrick1  Yeah I am with you both on your comments. 

As it is my blood I had the experiement anyway 😉   so whether I use my ISP DNS or my manually specified DNS or the Plusnet DNS Primary/ Secondary and their alternates . . . . . . still email is not working.  So I also now also wonder if the Plusnet DNS server is pointing at their own correct IP address.  So all put back to 'as was' and waiting for the guys to sort thier problems out.  It was worth the try but it is unlikely Plusnet will make a technical statement about the resolution.  Cheers both.

Baldrick1
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Re: Blocked email ports

Looking again at the email address make me wonder if it’s the full stop between the mail and defencegateway that’s causing issues.  My previous employer had their security set so that it it would not accept an address with a full stop before the @ as it can be used by scammers to mislead people to access scam sites.

Obviously that does not explain why it works with VPN, unless of course that is a MoD VPN with its own route in.

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Dan_the_Van
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Re: Blocked email ports

@ooogggle 

does nslookup resolve mail.defencegateway.mod.uk

it does for me I see using PlusNet dns and google dns

Non-authoritative answer:
Name: nlb-email-788480c833f2183a.elb.eu-west-2.amazonaws.com
Address: 18.133.210.238
Aliases: mail.defencegateway.mod.uk

Is 18.133.210.238 the expect IP Address?

using telnet I can connect to mail.defencegateway.mod.uk on ports 465 and 993

Dan.

ooogggle
Newbie
Posts: 3
Registered: ‎10-11-2021

Re: Blocked email ports

So magically all is working now..... The VPN was just a VPN into Azure so i came from Ireland, nothing to do with the domain.

 

Yep IP is right and the ports are now all open!