I am using Mandrake 9.2 and Evolution in which I have selected the Sendmail option. Up until 48 hours ago outwards mail worked fine. Evolution would forward to Postfix not Sendmail and it would go out without problem. Now no outwards mail is being processed. I can see the mail being queued in the /etc/spool/postfix/defer or deferred directories and can see that some of them have DNS resolution problems.

The only changes I have made to system is a new ADSL modem to replace one that lost its settings. The new modem has 192.168.1.1 has its address previous was 192.168.1.254
I have corrected the gateway address in Mandrake byt as stated above no mail is going out.
If I flick Evolution over SMTP at my DSL provider mail works fine but I prefer to retain the ability to handle my own email instead of relying on ISP.

I have tried restarting and flushing Postfix but the mail just doesn't move.
Any suggestions of where to look would be appreciated.

Have thought of trying qmail but where would I tell Evolution that qmail was my mailer. It only offers Sendmail or SMTP

You should be using the SMTP option. That's what postfix will use. I have a postfix server also and I set up evolution to use smtp. Thats how I set up clients also. I have really great postfix config also. I be posting a how to on my site within a week

And what do I put in Evolution as the smtp server Localhost or something?

You would put what ever the dns MX record has for your mailserver. Most folks use something like mail.mydomain.com . It needs to be listed in your dns though.

Sorry I did not make myself clear enough. I was talking of outwards smtp email. I have 'use sendmail' in Evolultion which causes outwards mail to be sent via Postfix smtp mail agent.
This has stopped working and I am trying to work out why.
I am not interesting in inwards email as I just pop that off my ISP.
Thanks anyway