I have one domain on my server and a mailbox (with the same domain ending) on a different server. I configured the mail and MX fields of DNS of that server to the proper value. All is working. But as I send an email from the website contact form (configured with SMTP = localhost) sending an email to the email address on the other server, the email will not reach the mail box ..Even no error is generated..Simply the mail server receives nothing. On the other hand from the contact form I can send email to different mailboxes.
How to solve this ?
I solved the issue by setting in the first panel for the SMTP settings in MailEnable, the host values to 200.x.x.x which should redirect all the traffic outside the server.
We have a IIS 6.0 server on AWS EC2 that is receiving emails and forwarding onto another IIS box, we are inadvertently sending NDR emails via the SMTP service to the forged From: header with the spam attached.
A few quick questions regarding IIS 6.0 SMTP
From reading we don't see a was to stop NDRs (this is by design to meet RFC requirements)
As we accept all emails sent to our address and process off line on a seperate machine can someone advise why NDR's are been delivered in the first place? Is there some other loophole they are using to force the SMTP server to generate Delayed and Non Delivery Reports?
Also can anyone recommend software that can stop this type of attack. e.g. Toriss, ORF from Vamsoft
You have to use SPF on the receiving machine so it does not accept mails with forged reverse-paths. There is no way to really fix the issue later in the mail server chain. (Note that the SMTP reverse path is not necessarily the same as the address in the From header, for example they always differ in list mails. If IIS does send bounce mails to the From address instead of the reverse-path then it is horribly broken.) If IIS does not know SPF, then you have to use a different mail server or an SMTP proxy.
I've installed Postfix, opened port 25 (as well as ports 110, 995, 143, and 993) on my local computer connected to the Internet, but none of the e-mails that I am attempting to send out using the localhost:25 definition are being properly routed to their destination. Basically, I am trying to set up a local SMTP server to send out e-mails from my production website's software (also hosted on the same local computer).
I am using Verizon FIOS Internet service, who reportedly blocks port 25 (but actually does not in my case, as I have enabled it and checked that is in fact accessible from my external IP address). I have attempted to send the e-mail using no Smart Host, then using Verizon's SMTP server as a Smart Host, and finally using Verizon/Yahoo's SMTP server as a Smart Host, but none of them have worked.
What could be causing this issue?
I really appreciate any help on this problem, because I've been working to no success on it for the past three hours. Thank you all in advance!
absolutely, it's very common for large ISPs to block outbound connections on port 25 ~ they do this specifically to prevent what you are attempting. You should give them a call and verify if this is the case.
OR
See if you can configure your postfix to authenticate on your verizon mail account and relay your mail through that. [actually I did exactly this ~ I'll see if I can dig up the config]
-sean
UPDATE
here we go:
relayhost = [smtp.gmail.com]:587
smtpd_sasl_auth_enable = no
smtp_sasl_security_options =
smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
Sorry, I'm a little crunched on time, you'll have to dig up the docs for postfix relaying and how to setup the password maps [cause I don't recall offhand]
Hope his helps...
Have you setup MX record in DNS (reverse DNS must work properly) and the respective domain name (FDQN) in the smpt demon ?
What kind of IP address does whatismyip.com provide?
How can I get it using VB.Net code?
Also what is IP port?
Thanks
Furqan
PART 1
Okay, let's pretend you have a router in your house and that you have several computers in your house all connected to the internet through your router.
In order for the router to know where traffic goes on your network, it assigns unique IP Addresses to all computers on your home network (Usually beginning with 192.168.x.x). These IP addresses are local ip addresses, meaning only your router and computers/devices connected to it in your house knows about them. If you open a command prompt and do command IPConfig you will see the IP address that your router has assigned your computer.
So what is the IP address that WhatIsMyIP.com showing you? In much the same way that your router assigns addresses to all the computers on your network, your internet service provider hands out unique IP addresses to all of their customers. Now, because you have a router, the only thing the ISP can see on your network is that router and your ISP assigns an IP address to it. This is why routers are also called hardware firewalls, because people on the other side of it, can't tell how many computers or devices are connected to it.
What this means is, when you are visiting websites on the internet, the only IP address they see is your routers external IP address (the one assigned by your ISP). So no matter which computer in your house you use, the website wouldn't know the difference because all it can see is your router's IP address. Go ahead and try it; go to www.WhatIsMyIP.com on several different computers in your house. You will see that they all show the same IP address. However, if you did IPConfig in your command prompt on each computer, that shows you the local address your router assigned and it would be different on every computer in your home.
So, now that you understand the difference between local and external IP addresses, how would you retrieve your external IP address in VB or C# .net code that is running on your PC? Well the only IP address your computer is actually aware of is that local IP that we talked about. The only way you can see your external IP address is to go to a website that tells you what address the request came from (which would be your router's IP address).
What you would need to do is write up some code in your VB.net program that would navigate out to WhatIsMyIP.com (or some other website that can give you your IP address) and tell the code to grab it. I have written a web service located at http://www.u413.com/test/terminal/myip that returns only your IP address as the entire HTTP response. Find something similar though for your application because this little sample will not stay there forever; I only put it up there as a temporary example on a domain I already own.
Visit http://www.vbdotnetheaven.com/UploadFile/kbawala/WebRequestClass04182005054320AM/WebRequestClass.aspx to see how to make web requests from code running on your computer.
NOTE: You may not be aware of what DNS is either if you are unaware of how IP addresses work. Everything on the net has an IP address, including the servers that serve up website pages. But what a pain that would be, trying to remember up to 12 digit IP addresses for all your favorite websites. That is what DNS servers were invented for. DNS servers take a domain name (e.g. www.facebook.com) and translates it into the correct IP address. That way all you need to remember is facbook.com instead of 69.63.181.12 (this is facebook's IP address. Go ahead, try it! Put that IP in your browser's address bar and you will see facebook.), domain names are much easier to remember!
If you want to see the IP address associated with a website, open up a command prompt. Once the prompt is open type PING [websitedomain] (e.g. PING Facebook.com) and your computer will send 4 test requests to the address which is displayed for you.
PART 2
Let's pretend your IP address is like the address of an apartment buliding. The pizza delivery boy needs to know the address to the apartment building in order to deliver your pizza. But what is he going to do when he gets there? There are hundreds of doors/apartments to choose from. He needs to know the apartment number (port number on your computer).
Your computer has thousands of ports, and programs can listen on any one of them for requests from the outside world. When you go to a website almost all websites are served on port 80. Port 80 is the default port for web pages. When you go to facebook.com you are actually going to facebook.com:80, you just don't see the :80 because it is implied since it is the default. If I put up a web server, I could decide any port to serve websites on. If I served web pages on a different port than port 80, then you would have to include it in your URL. http://www.SomeDudesCustomWebServer.com:1337.
Outgoing requests use a port too, but that one is usually unimportant and your computer just picks one that is available. So when you go to Facebook.com, the facebook web servers are all serving up pages over port 80, but the port your computer opened up to send the request does not have to be port 80 because it picks an available port and then sends the port with the request. Then when facebook sends its response, it sends the reply back to the ip address and port that made the request.
Outgoing ports are only used for the duration of the request. Ports that must listen for connections must stay the same otherwise the computers making requests would have no idea what port to send the request to.
Easy huh!
Hope that helps you understand a bit better.
EDIT:
Port Forwarding
Okay, in light of the chat application you want to use/create, if you want it to communicate over the net you'll have to learn about port forwarding. Basically, because all you could see of your friend's network would be his external ip address, you will have to use that address to connect to his chat server (or vice versa if he is connecting to your chat server then it will be your external IP). Because of this, the connection request would only get as far as the router that has the external IP, but it would not know what computer on the network to forward the request to.
You will need to access your router's firmware and set up port forwarding so that the router knows to forward requests on a specific port, to a specific computer on the network. Visit http://portforward.com/ for more detail on how to setup port forwarding.
EDIT 2:
Firewall
When setting up stuff to communicate with your computer using your PC, you may start getting frustrated that it just won't connect. What is likely stopping you is your firewall. By default, most ports on your PC are completely blocked by the windows firewall. For each port that you want to communicate on you will want to go into the firewall and create a rule that will open up the port. Go here http://www.top-windows-tutorials.com/windows-7-firewall.html for a video on how to use the windows firewall. I did not watch it, but it is what came up first on a google search.
Do not simply disable the firewall. Even though this is an easy and quick solution to open up all your ports, you are leaving yourself open to attack. Viruses love to set themselves up in your computer if they can and listen on an open port for a connection from their beloved creator so he can obtain access to your PC. Only open the ports you need.
UDP vs TCP
When opening and forwarding ports you may notice that it asks for UDP (User Datagram Protocol) or TCP (Transmission Control Protocol). What they stand for may not make sense but all you need to know is this: UDP is for single packet transmissions which means that two packets sent by a pc may or may not be related to each other. These types of data packets are usually used for broadcasts on a local network. An example I would use is LAN games. When you host a game on a LAN the other computers/devices can see the name of the game and join it. That is because the computer hosting the game is transmitting a UDP broadcast across the entire LAN so that any devices can see the game. Those UDP transmissions usually contain the name of the game and the connection info required to connect to the game.
TCP is for continuous packet transmission. TCP requires an established connection, any packets transmitted on this connection are always related to that one connection/request. To continue my example from the last paragraph, once you click connect on the LAN game, your computer then establishes a TCP connection with the host and uses that connection for the duration of the game or games. TCP is the most commonly used connection type and your chat program would likely communicate over TCP, especially if you are connecting across the net because UDP broadcasts are useless across the internet. UDP is only really useful on a LAN.
You should be safe forwarding and unblocking only the TCP ports, but sometimes when I'm unsure I just do both UDP and TCP just to be safe. In fact, many routers and firewalls have 3 options: TCP, UDP, or Both which saves you from having to create two rules for both types of the port.
When in doubt, open/forward both.
What's my ip provides your IP v4 public address.
It's really easy to retrieve it, this topic explain how to proceed : How to get the IP address of the server on which my C# application is running on?
The code is only a few lines long, so the language (c# in this example) does'nt matter.
They provide your external internet facing IP.
This IP will depend on how you connect to the internet. If you connect straight from your computer to your ISP without any kind of router or firewall in between, it might be the same as your internal IP, but in most circumstances this will not be the case.
If you're at home and you've connected via a router of some kind, then you might be able to query it for the IP, but there is no standard way of doing this.
There is no standard way of getting hold of your external IP from the client it self. If you've got access to a server on the internet where you could deploy some code you could connect to that server from your client PC and ask it what IP you're connecting from.
IP Port Numbers
I also needed external IP using command line, but because I didn't find it I wrote small application using vb.net. You can use reflection for source code or ask on app home page for it. Basically application opens web page that provide your IP and parse it using regular expression, but because is designed with this purpose uses many "tricks" for this (can use more web pages at once, uses fastes page, etc). Check source for details.
internally, our organization limits what servers and applications can send emails. I would like to be able to have scripts that could be run on any server send an email when done. Is it possible to install IIS SMTP on a single server and have that relay all mail the servers send to our standard relay servers? All the advice I see on the internet talks about configuring relays for outbound connectivity, but this would be for internal use only. the flow would be something like this, I believe
[any server] --> My SMTP relay --> corporate SMTP relay --> Internal Mail system
Is this doable? if so, any links on how to configure? I have nearly zero SMTP knowledge.
Doable, you should search for "SMARTHOST SMTP" in google. If your mail server limits relaying to specific HOSTS/IP address, you'll still need to add the new server to the relay list. Setup will be a little different depending on you mail server/version (Exchange, IIS SMTP).
SMART HOST for Exchange:
http://www.dnsexit.com/support/mailrelay/exchange/setup.htm
I have a similar setup to what you have described. You might want want to check if your SMTP server allows relaying for authenticated users, since this might allow you current script to send emails using a domain/email user account.