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ISP Blocks port 25 what options do I have?
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ISP Blocks port 25 what options do I have? - 31.Dec.2008 1:38:14 PM
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hevnbnd
Posts: 21
Joined: 4.Sep.2007
Status: offline
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Ok, I have been researching this for a while now. I manage 3 exchange servers for clients and decided to build one here at my house. My ISP blocks port 25. I guess the easiest solution would be use No-IP.com or dyndns.org and use their mail reflector service. Both will will redirect your mail to your server on any port you choose (for a fee). That is the option that will cost me money. However I have also read about option 2 which confuses me in its setup.
The basic idea was:
- Point public MX records at your server
- Setup your server to point to a DNS server which has a different
version of the zone, stating the correct MX server IP
- Have your server accept mail for the domain, on a relaying basis
(bridgehead if you will)
At this point, mail will come through you, to their server. Then the
magic..
- Set your firewall to redirect connections from your server, to their
server's port 25, to their server's port 26.
- Set their firewall to accept incoming mail in port 26, and relay it
to port 25 internally.
At this point, the user can receive email as though they were
receiving it directly. And then..
- Have their server set to route all outbound email through yours
- Their firewall changes to destination port to 26
- You receive on port 26
Will option 2 work? Anyone used it? Any tips on setting it up? Thanks for your time.
< Message edited by hevnbnd -- 31.Dec.2008 1:42:16 PM >
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RE: ISP Blocks port 25 what options do I have? - 31.Dec.2008 1:47:37 PM
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mark@mvps.org
Posts: 6811
Joined: 9.Jun.2004
From: Philadelphia PA
Status: offline
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If your ISP is blocking TCP 25 or SMTP (some block the port, some read the traffic and block the protocol on whatever port it's jury-rigged onto) you should just use a POP3 connector. Have all your mail delivered to an ISP account (gmail?) and use the connector to pull the email down. The connector will then shove traffic onto your Exchange server over SMTP.
Outbound email is a little more tricky. Your ISP //WILL// have an SMTP relay that they must allow you to use so the worst you'll have to do is to configure your send connector on Exchange to authenticate to that smarthost. If you're lucky your ISP will just let any SMTP flow through their relays without authentication because they know it's from their subnets.
Don't even think of trying to spoof anything or generally muck about. Just use the connector based solution and your ISP will be no wiser. All they will see is POP traffic to get the mail and SMTP traffic to send it - via their servers. Nothing contentious, nothing dodgy.
_____________________________
Mark Arnold (Exchange MVP)
List Moderator
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RE: ISP Blocks port 25 what options do I have? - 31.Dec.2008 4:55:14 PM
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hevnbnd
Posts: 21
Joined: 4.Sep.2007
Status: offline
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I thought pop 3 was the worst way to go. I would actually go as far as to say that POP3 is the last remote access method of choice for Exchange as it basically turns Exchange in to nothing more than a POP3 service that you can get from your ISP for free! that was a quote from Simon Butler,
Exchange MVP on the subject...
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RE: ISP Blocks port 25 what options do I have? - 31.Dec.2008 5:08:36 PM
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mark@mvps.org
Posts: 6811
Joined: 9.Jun.2004
From: Philadelphia PA
Status: offline
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POP3 is the 2nd worst way to go. Sticking with an ISP that won't let you have TCP25 into your server is the worst way to go. And Simon is right about the POP3 turning your Exchange into no more than you'd get from a POP3 service on the Internet. Being an Exchange MVP as well, I'd naturally agree with SB.
If you do the whole forwarding and then bouncing to TCP 26 you're possibly violating the terms of use with your ISP. If they're blocking TCP25 you might say that you're within the letter of the law to change to 26 but you're not following the spirit and they could bounce you just as well.
My advice to you is to do one of these things:
1. New ISP
2. Change your terms of service with the ISP to allow TCP25 / SMTP (make sure you specify port and protocol - don't leave it to "everyone knows TCP25 is SMTP", because it doesn't /have/ to be.
3. Do the POP thing to get your mail and use the ISPs relay/smarthost to send your mail out.
I would steer a long way away from bouncing mail around different servers and/or ports.
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Mark Arnold (Exchange MVP)
List Moderator
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RE: ISP Blocks port 25 what options do I have? - 31.Dec.2008 6:27:38 PM
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hevnbnd
Posts: 21
Joined: 4.Sep.2007
Status: offline
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So how do I get my isp relay/smarthost? I called them and they said that is only for bussiness customers and that even if I setup a smarthost email with my buis account it would not work with a home server.. I am not sure I believe them. I am a little green on the subject if you can not tell.
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RE: ISP Blocks port 25 what options do I have? - 1.Jan.2009 11:29:44 AM
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mark@mvps.org
Posts: 6811
Joined: 9.Jun.2004
From: Philadelphia PA
Status: offline
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OK. Bottom line is that you may need to forget this, at least doing it from home. You can do all the testing you need at home with your Exchange server. You can POP messages into an app which delivers them to your system over SMTP and you can 'send' messages out. Sure, they'll just sit and queue up because they have no way out.
And the whole ISP not letting you relay is nonsense. Every ISP will give you instructions on how to configure Outlook Express (since it's the most ubiquitous client) to receive mail from their @isp.com mail servers and there HAS!!!! to be an SMTP server because you don't send with POP, only receive. So you're right in that they aren't telling you the truth. It's probably that you've been rumbled or you've unwisely asked and used "Exchange". You should have just asked for the Outlook Express settings. You can easily take the host name and whether or not you need to authenticate and take that information to plug into Exchange.
If they won't give you any SMTP details, leave them.
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Mark Arnold (Exchange MVP)
List Moderator
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RE: ISP Blocks port 25 what options do I have? - 1.Jan.2009 1:07:49 PM
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Sembee
Posts: 4093
Joined: 17.Jan.2008
From: Somewhere near London, UK
Status: offline
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I actually have another solution.
I am going to blog on this after I have tested it, but it should work.
Mail Foundry have a hosted spam solution which is currently free for the first ten mailboxes.
If I have read the instructions correctly, they can forward your email to another port. Therefore you have your MX records pointing to them, then they send email to you on a port that is not blocked by your ISP. Outbound email goes via the ISPs SMTP Server as already outlined.
I haven't tested the MailFoundry system, it was something I was planning to do soon, but it will not do any harm to get an account and have a look around.
I was also misquoted. When I make references to POP3 with Exchange being nothing better than what you get from your ISP, I am referring to the use of the POP3 server in Exchange (ie not using Outlook to connect to Exchange as a MAPI client). What Mark was referring to was using a POP3 connector to collect email from the ISPs POP3 mailboxes. You still get full Exchange functionality, just with the drawbacks of using a POP3 connector.
Mark - you don't always have to agree with me, particularly now you are a few thousand miles away!
Simon.
_____________________________
Simon Butler,
Exchange MVP
Blog: http://blog.sembee.co.uk/
Web: http://www.amset.info/
In the UK? Hire me: http://www.sembee.co.uk/
Exchange Resources: http://exbpa.com/
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RE: ISP Blocks port 25 what options do I have? - 1.Jan.2009 3:21:02 PM
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mark@mvps.org
Posts: 6811
Joined: 9.Jun.2004
From: Philadelphia PA
Status: offline
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That sounds like a nice solution for inbound. Might check it out myself as it happens. The OP still looks like he's going to have a battle on his hands with the ISP though. His post timed at 11:27 is weird in that they'll give him the SMTP details only for a business based account. Barking mad if you ask me unless they simply don't want to be bothered with people at home which makes no sense if they're selling to home based users.
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Mark Arnold (Exchange MVP)
List Moderator
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RE: ISP Blocks port 25 what options do I have? - 1.Jan.2009 8:35:41 PM
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Sembee
Posts: 4093
Joined: 17.Jan.2008
From: Somewhere near London, UK
Status: offline
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We all know what ISP tech support is like. Close to useless, looking to close a call with "not supported". If they are selling to home users then there will be an outbound SMTP server that can be used. The only drawback might be that it is restricted to email in their own domain.
You might be able to send email OUT through Mail Foundry, I need to look at it carefully to see.
Simon.
_____________________________
Simon Butler,
Exchange MVP
Blog: http://blog.sembee.co.uk/
Web: http://www.amset.info/
In the UK? Hire me: http://www.sembee.co.uk/
Exchange Resources: http://exbpa.com/
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RE: ISP Blocks port 25 what options do I have? - 4.Jan.2009 11:25:56 PM
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hevnbnd
Posts: 21
Joined: 4.Sep.2007
Status: offline
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Ok, I have decided to go this route since I pay for a buis account at my office and a home account at my home from the same isp. I have static ip at both locations. I pointed my mx records for my homeemail.com to the same ip that is on myworkemail.com. At my company I set up a 2nd Send Connector, Receive Connector, & Accepted Domain in exchange 2007. I finally got this working after much trial and error. Any reason's why I do NOT want to do this?
< Message edited by hevnbnd -- 5.Jan.2009 12:10:41 AM >
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RE: ISP Blocks port 25 what options do I have? - 5.Jan.2009 6:07:04 AM
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Sembee
Posts: 4093
Joined: 17.Jan.2008
From: Somewhere near London, UK
Status: offline
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The main one would be that you lose the ability to filter out invalid recipients. The server that receives the email for the domain at home would accept all email and then attempt to pass it on. Rejecting invalid recipients can cause a significant percentage of garbage email to be rejected. I have a site that rejects almost two thirds of email delivery because they are sent to invalid recipients.
Simon.
_____________________________
Simon Butler,
Exchange MVP
Blog: http://blog.sembee.co.uk/
Web: http://www.amset.info/
In the UK? Hire me: http://www.sembee.co.uk/
Exchange Resources: http://exbpa.com/
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