Host email server w/o static IP

[HKNinja]

Can this be done on Fedora, anyone?


- Harry

 

[zeland]

You send email in the form, user@domain. Thus it is more important that you have a static host/domain name rather than a static IP. If you need to host email on a dynamic IP, go get yourself an account at dyndns.org or tzo.com.

--== Anything can go wrong. It's just a matter of how far wrong it will go till people think its right. ==--

 

[RhythmAce]

Most servers, whether we are talking about web, mail, ftp or anything else, are configured by default to listen for all addresses on one specific port. The only reason for changing this in most cases is if there is more than one interface on the host server. In that case you would set it to listen for the ip address of the interface you want such as eth0, eth1, etc. So to get mail to come to your server, you need a static ip address or use a pointer service as zeland has suggested. Keep in mind however that you will have two strikes against you in this case. To send mail, email protocol requires a return route. If there is no DNS "MX" record, most recieving mail servers will reject the mail. The other thing is that this is the type of return address that most spammers use. You will find that many ISPs may accept your mail but put it in the user's spam folder. You just have a lot of flags that anti-spam software looks for. That being said, you can run a mail server with a dynamic ip. It will be very limited though and may work fine for a small circle of users but would not be recommended for a production server.

 

[QatQat]

Well I 'd like to disagree a bit with RythmAce

Most dyn dns services these days will keep your MX record as a CNAME and will update the "IN A" record related to your mail server so the DNS check performed by servers when receiving messages from your server will be just fine.

I may say that, for vital application, your Dynamic IP hosting is just as available as your ISP address reset policy. If you have a "non paranoid" isp that will reset weekly and at night, then you can assume that you will not drop any messages. Normally servers will try for 4 hrs to resend messages, so even if dropped initially you may still get the message with a bit of delay.

Another point to be highlighted concerns not your server but sender's DNS server.
On Master DNS servers you record will be updated quite quickly; on caching only it will be updated, if they already have a record for your domain, only when the TTL (time to live) is expired (normally 24hrs but it is becoming more frequent to shorten it, mine is 7200 sec)

So the reliability of hosting email services on a dynamic address depends on a lot of factors that you have to take into account.

Also RythmAce mentioned anti-spam software putting your message in the spam folder if coming from DynIP. Well, normally (not always) that check is no job for an anti-spam software; IP check happens rather at DNSBL level, which anyway needs spam to have been sent from your address bofore listing you. So if your server is secure and relay not allowed or properly controlled, messages will be accepted by a receiving server once the reverse DNS check is fullfilled, and the message will be examined in its content only (but seldom further Ip check may occur as RA mentioned) by a spam filter.

To verify if servers will reject your messages you may test the mail transation by doing it manually

telnet serveraddress 25
helo yourserver FQDN

If you pass this stage then spam filters will only block your message if it is spam.

So I would not be that concerned.

Having said so, I also prefer to use a static adress for my server but DynIP is way cheaper for "non critical" mail servers. I use it on a number of servers around the country
without problem.

QatQat


If I could have sex each time I reboot my server, I would definitely prefer Windoz over Linux!