Troubleshooting Email problems or Fun with DNS MX Records

Recently I added SSL to my google app engine account and I had to change my DNS settings to facilitate this. Unfortunately this caused an issue with my mail delivery.

I thought I'd write up a short note on how I repaired it in hopes this will save someone else some time.

If you're not getting the emails you expect, the first thing to check is your DNS config. I'm going to assume you have a UNIX environment. I have cygwin on windows. Open nslookup app:

$ nslookup
Default Server:  google-public-dns-a.google.com
Address:  8.8.8.8

> set q=mx
> fullrank.com.
Non-authoritative answer:
Server:  google-public-dns-a.google.com
Address:  8.8.8.8

fullrank.com    MX preference = 10, mail exchanger = mx2.daemonmail.net
fullrank.com    MX preference = 10, mail exchanger = mx1.daemonmail.net
> quit

So we see here that the mail settings are fine. If you don't have any DNS mail exchanger or "MX" records, (I didn't) then you need to go to your registrar and add these records.

Note that the DNS server that I was querying for this was my local provider, google (IP address 8.8.8.8). Typically any changes to your DNS records take some time to propagate to your DNS provider and then take an additional period to move to other DNS servers around the world. Using the "server" nslookup command will allow you to see changes more quickly.

$ nslookup
Default Server:  google-public-dns-a.google.com
Address:  8.8.8.8

> server ns1.domaindiscover.com
Default Server:  ns1.domaindiscover.com
Address:  216.104.162.3

> set q=mx
> fullrank.com.
Server:  ns1.domaindiscover.com
Address:  216.104.162.3

fullrank.com    MX preference = 10, mail exchanger = mx2.daemonmail.net
fullrank.com    MX preference = 10, mail exchanger = mx1.daemonmail.net
mx2.daemonmail.net      internet address = 216.104.161.5
mx1.daemonmail.net      internet address = 216.104.161.4
> quit

So now we see that the DNS is correct but what about the mail servers? We can send email directly from telnet:

$ telnet mx2.daemonmail.net 25
Trying 216.104.161.5...
Connected to mx2.daemonmail.net.
Escape character is '^]'.
220 mxw04.daemonmail.net ESMTP Postfix (Ubuntu)
MAIL FROM: foo@bar.com
250 2.1.0 Ok
RCPT TO: foo@fullrank.com
250 2.1.5 Ok
DATA
354 End data with .
line1
lin2
.
250 2.0.0 Ok: queued as AA5E4FFB32
quit
221 2.0.0 Bye
Connection closed by foreign host.

$

We see that the email was accepted. This doesn't mean that everything is fine but likely, you're most of the way there.