Thursday, 3 May 2007

Exchange SMTP Problems

Checking you email server setup is a very importent because its better than having users telling you they are not able to send email, and that's just one reason.

You can check your domain name record by doing a domain name look up also called a NSLOOKUP here is an example lookup.

C:\Documents and Settings\Administrator>nslookup

Default Server: ns.isp.co.uk
Address: 195.186.44.13


> set query=any

> domain.net
Server: ns.isp.co.uk

Address: 195.186.44.13

domain.net

primary name server = server.domain.net
responsible mail addr = admin.domain.net serial = 2007032026
refresh = 1800 (30 mins)
retry = 900 (15 mins)
expire = 604800 (7 days)
default TTL = 3600 (1 hour)

domain.net nameserver = ns2.isp.co.uk
domain.net nameserver = ns.isp.co.uk domain.net
MX preference = 10, mail exchanger = server.domain.net domain.net
MX preference = 20, mail exchanger = smtp.isp.net domain.net

text = "v=spf1 mx ~all"

ns.isp.co.uk internet address = 195.186.219.229
ns2.isp.co.uk internet address = 195.186.218.7
server.domain.net internet address = 195.186.174.123
smtp.isp.net internet address = 195.186.131.8
>

Now you check your mail server has a revise domain name record setup, if it doesn’t the some mail server such as AOL and Yahoo and others will not accept email from you.

>set query=ptr
>195.186.174.123
Server: [195.186.44.13]
Address: 195.186.44.13
Non-authoritative answer:
123.174.186.195.in-addr.arpa name = server.domain.net

174.186.195.in-addr.arpa nameserver = ns.isp.co.uk
174.186.195.in-addr.arpa nameserver = ns2.isp.co.uk
ns.isp.co.uk internet address = 195.186.219.229
ns2.isp.co.uk internet address = 195.186.218.7
>

Make sure you FQDN (Fully Qualified Domain Name) on the server matches the MX record; you can do this by telneting to your mail server.

telnet server.domain.net 25

You should see a response like.

220 server.domain.net Microsoft ESMTP MAIL Service, Version: 6.0.3790.3959

If you receive a response like the one below then you’ll need to make some changes as it is also a technical violation of RFC821 4.3 (and RFC2821 4.3.1)

220 domain.net Microsoft ESMTP MAIL Service, Version: 6.0.3790.3959

If you follow all these rule you should be able to email anyone and everyone.

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