This applies to you if you are a company doing marketing via e-mail shots.
Normally associated with larger companies:
1) If your domain is acmeproducts.co.uk and you send your marketing e-mails from @marketing7.co.uk it already looks like spam.
2) If the links in your e-mail don't link to your primary domain (e.g. www.acmproducts.co.uk/tracking/abc1294890384098014.htm vs www.marketing7.co.uk/tracking/abc1294890384098014.htm) it looks just like a phishing e-mail to me and anyone who has the sense to avoid phishing traps.
And the biggy, but with smaller companies:
3) If you send out an e-mail to a number of people who are your marketing database, DO NOT INCLUDE ALL OF THEIR E-MAIL ADDRESSES IN THE E-MAIL. It leaks your marketing database, it puts my e-mail onto spam databases, assuming that one of those 100 odd accounts is compromised, it tells people I have no association with something about me.
So rant over. Now I feel a lot more chilled. Have a nice day.