Hoople - 10:54 pm on Jan 6, 2013 (gmt 0)
Use a different domain for sending emails or a mailing service that allows you to send individual emails.
I agree a thousand percent to the above. If you inadvertently get blacklisted all you loose is the marketing-example.tld domain.
There are a number of products out there to do marketing mailings that handle both global and site specific throttling. Some do number of messages per hour/time between messages. cPanel is by default set to 300 per hour IIRC.
Yahoo also tags mail as SPAM if more than a certain amount come from a single source over a finite time. Choice of specific SMTP server also influences SPAM scrore, especially if your sending IP is in a 'portable' range.
It goes without saying if you are going bulk sending that not being spam is your personal opinion. Do consider making Opt-Out a single click even if your country doesn't require it. [spamlinks.net ] Read carefully the country specific regulations. Read the postmaster pages on AOL, Yahoo!, Comcast and any other major ISP's named in your target recipients.
With some ISP's read their whitelisting process as it may mean the difference between being delivered to the user's spam folder vs their Inbox. [postmaster.aol.com ] [help.yahoo.com ]