I sent out a promo to my opt-in list the other day and got virtually no response. This is very uncharacteristic of the list, and I wonder if my server has been blocked, but I haven't received any notification.

In addition, I ususally get a LOT of email responses, but this time, I got three (list is 6K+).

How can I know if I, for whatever reason, have had my server blocked?

Were you using a link in your email letter, if so it might be on the RBL list. You can check spamhaus to see if your mail server IP has been blocked, a lot of ISP's are now using there database to fight against spam. Were you using the mail server of your ISP? Hosting company? Third party SMTP? Did you send yourself an email to an email account that has spam assassin installed on it to check the spam assassin score? Anything above 5 will trigger spam assassin and your mail will not go out.

Who are you sending to? Many ISP use internal block, and some have unblock forms.

A good place to start would be to check your uribls and surbls

http://www.rulesemporium.com/cgi-bin/uribl.cgi

To see if your server has been blacklisted simply go to the following page and enter the email server's ip address.

hXXp://w3.m*xtool*box.com/black*lists.aspx?AG=GBL