My warnning on using a mail server with a dynamic ip.

[usalabs]

It seems nobody is warning people about attempting to use mail servers with a dynamic ip, well, here's my warning.

This is to warn ANYONE that want to use a mail server with a dynamic ip address and expect it to work, it DOESN'T, the reason being, every reputable mail domain (MSN, YAHOO, GMAIL, ETC ETC) WILL refuse emails sent from a dynamic ip, because they expect the reverse dns to point to the mail server that's sending emails, and dynamic ip's WILL always point to the ISP.

EG.

domain = test.com, dynamic ip = 1.2.3.4
reversedns = 1-2-3-4-isp-domain.

domain = yahoo.com, static ip = 216.109.112.135
reversedns = w2.rc.vip.dcn.yahoo.com.

So, that means it IS! IMPOSSIBLE to run an emal server using a dynamic ip address, it doesn't matter if a dynamic dns service is used, a dynamic ip's reverse dns will ALWAYS POINT TO THE isp DOMAIN.

Summary:
DO NOT WASTE TIME IN TRYINNG TO SET UP A MAIL SERVER WITH A DYNAMIC IP.

BUY A STATIC IP.

[wkeys]

hi
Good point thanks for the warning.
~Bill

[scrumpy]

usalabs,

yep, big problem.

although this link is a paid service it is cheap, I wonder if it would overcome the problem?
http://www.dyndns.com/services/mailhop/outbound.html

[usalabs]

I should have also included, that it is possible to receive emails using postfix but impossible to send them.

[usalabs]

usalabs,

yep, big problem.

although this link is a paid service it is cheap, I wonder if it would overcome the problem?
http://www.dyndns.com/services/mailhop/outbound.html

Unfortunately, dynamic DNS services don't have a reverse DNS record that's editable by a user, I use afraid.org, and my reverse DNS still points to my ISP, even though I set up all required A, MX and SPF records.

A lot of the dynamic DNS services are aimed at mail hopping, or web forwarding to another port, ie, an ISP blocks incoming port 80 (HTTP port), a user then sets up his server port to another port that isn't blocked, then sets up the dynamic DNS web forward to send all incoming http requests to that port, so when someone uses a standard url, the incoming http request (usually on port 80) get routed to the unblocked port, before it travels through an ISP firewall.

Unfortunately, there is no (free) workaround for sending emails from a home server using a dynamic IP.

[pmstewart]

It is possible to use your internet service provider's email server (if they support open relay from within their own network).

Examples of this in my area are comcast.net and qwest.com

To do this your server software has to provide for sending mail though a registered mail account.

In Use:

1. setup an email account with your provider (most allow 5 or more with your internet subscription)
if your domain name is "domain" then create an email address which is similar such as "domain"@internetserviceprovider.com

2. forward the outgoing mail from your engarde box to this address and enter the username and passwsord assigned to "domain"@internetserviceprovider.com

This will bypass the dynamic ip issue since the emails are now coming from your upstream provider and all works well.

Good Luck