Blocking email services from the router

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Jin0

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Hi, I have a wifi router which is shared by several cell phones. What I want is to block these cell phones from using email services such as Yahoo and Gmail and to block specific websites changing my router's settings. I read that this depends on the router's features and the following are the options available in two relevant sections of my router's setting.

The first one is a "filter section" which has options such as filter selection (IP filter/MAC filter), policy (accept/drop) source IP address and destination IP address (with mask value included), Protocol (Both/TCP/UDP/All), Destination port (from xxx to xxx).

The second one is a "port forwarding section" with the options such as protocol (Both/TCP/UDP), incoming start port, incoming end port, forward start port, forward end port, and destination IP.

I'd be very grateful if anybody can explain me what values I have to write in or choose in the above sections to block email services and specific websites.

Thank you in advance.
 
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bill001g

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It likely is close to impossible without making thing very painful for them. There are multiple ways to access a gmail account and some are easy to block but if you just use a simple web browser to access them that is very hard to prevent. Used to be you could filter certain traffic now that google is encrypted you would almost have to completely block google....which is hard to do and would make many things not work. Most andriod phone have may dependencies on accessing things at google.

I suspect yahoo is similar.

I would hope you have just set the option to not allow remote administration of the router from the internet. That should prevent any one from even being able to attempt it. If you need to admin it from the internet there is usually a special screen you can put in allowed ip address. It tends to not be in the same area you limit user traffic.
 
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Jin0

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Thanks a lot for your quick reply.
I'm sorry for not being clear. It's ok if they have access to them through a web browser. What I meant by email services were those like imap and pop3. I think I could do something to stop these with blocking some ports and ip addresses in the above two sections I described earlier. Can you please tell me what I have to type in those options to block these ports?
 
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bill001g

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Rather than retype what this site has explained I will link it, they have a list of the ports and what they do. The only addition might be TCP port 587

https://www.siteground.com/tutorials/email/pop3-imap-smtp-ports.htm

It varies a little from router to router. Some you must assign the ip or mac to block to a group and then block that group.

In the simplest case ...lets say the you have cell phone x with ip 192.168.100.100 and you want to block say port 993

You would put in a rule that says

block 192.168.100.100 mask 255.255.255.255 to any-site port tcp 993

I think all but port 25 is tcp which uses udp. You would need to put a number of rules blocking all the common ports. This sample rule blocks imap to all sites for ip 192.168.100.100, if you actually wanted to block just gmail and yahoo you would have to search for a list of ip they use as servers and key in rules for each. It maybe easier if there are valid mail servers to block them all and then put in a PERMIT ----to host x.x.x.x rules in that overides the deny.
 
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Jin0

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Thank you for the link!
I found QoS setting in my router which allowed me to reduce the speed to as low as 1 kbps by specifying the IP address, Protocol and port ranges only. I referred to the link you provided to reduce the speed of the imap, POP3, and smtp services and the email reception and transmission became very slow. The good news is I can control the speed of the ports just by specifying the port numbers and local ip addresses only.
But what I wanted was to CLOSE those ports completely. The problem of the filter setting is I still have to define the destination IP addresses (e.g. those of imap and pop3) which, as you said earlier, would include several, not one.
So my question is if there is any way I can close the ports of imap, pop3, and smtp without specifying the destination ip address. I read somewhere that I could use port forwarding by setting a port forwarded to an ip address I don't use but this wouldn't work, perhaps I couldn't do it properly.
How can I simply close those ports?

By the way I wanted to post pictures of the setting page of my router here but I can't chooses the one in my hard disk. I'm only allowed to post the url address of the image. What should I do to post images here?
 
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