A customer contacted us a few days ago with an email dilemma. They had been receiving a valued daily report through email, and all of a sudden they stopped receiving it and found that it was in their spam filter and wondered why.
After taking a look at it, it turns out that the sender had changed their "from" address for their bulk email. Just about all bulk mail (spam if you don't want it, bulk mail if you do), will get flagged by spam filters. The recipient had already "safe listed" the old address, but with the new address, it was getting stopped again. This was easily fixed by updating the safe sender list to include the new address.
In your own small business, if you send out a newsletter or other sort of daily, weekly, or monthly update, keep in mind that many of your recipients may find it valuable and want to receive it, but spam filters may stop it. Think carefully before changing your "from" address, because many of your recipients may stop receiving it if you do!