Thank you Chrism01 and Ser Olmy for your help. I will make this quick response and then pursue your suggestions further.
I am trying to use a CNAME. Not by choice. I am trying to host multiple domains on my home server which has a dynamic ip. All I could get to work was to have a no-ip domain name to which I point the CNAME of my domain at 1and1 and then use the nginx virtual domain feature. It seems to be working, though: before I set up the mail server I sent an email to
webmaster@mydomain.com and received this message in return from my host gateway:
<webmaster@sticky.no-ip.org>: connect to
sticky.no-ip.org[my.ip.addr.ess]:25: Connection timed out
The ip address was right. Now that I have the server installed I havn't received this return notice in response to my most recent email.
There don't seem to be any log files which concern mail on the server. I have been sending my test emails from FastMail. I will try disabling spamassassin and postgrey. tcpdump isn't a command on my system, I assume I will have to install it. I can telnet into port 25 from my workstation, though I don't know what to type after I am in to test anything. I will investigate that further.
So, thank you again. I appreciate your help. If you have any more insights I am all ears. I think I might already have enough to take me to the next level, though, and you have my gratitude.
correction: I did just get a failure message from my most recent email although this time the message is from my own server I guess:
This is the mail system at host
www.mydomain.com.
####################################################################
# THIS IS A WARNING ONLY. YOU DO NOT NEED TO RESEND YOUR MESSAGE. #
####################################################################
Your message could not be delivered for more than 4 hour(s).
It will be retried until it is 1 day(s) old.
For further assistance, please send mail to postmaster.
If you do so, please include this problem report. You can
delete your own text from the attached returned message.
The mail system
<webmaster@localhost> (expanded from <webmaster@mydomain.com>):
temporary failure. Command output: pipe: fatal: pipe_command: execvp
/usr/bin/perlbin/vendor/spamc: No such file or directory
There are also some attachments. I will look into this.