ISP’s (Internet Service Providers) are increasingly adding pools of their dynamic (consumer) ip addresses to the Spamhaus database, with a policy that any email coming from these ip addresses must use that ISP’s designated email servers. What this means is that if you are sending email from your home computer through another email service, and using an email client, the email may be rejected if a spam filtering system is using the Spamhaus database. Internet Service providing companies (Verizon being one of the largest) are resorting to this policy because of the number of virus-infected consumer PCs that are sending out spam.
If Redtail is hosting your email, and outbound email you send from home using an email client (such as Outlook or Thunderbird) is not making it to your clients, using Redtail's webmail client when sending messages from home should resolve the issue. If you're experiencing the issue and using webmail does not resolve, please contact Redtail's Email support team and we'll be happy to troubleshoot further for you.