Why am are my emails being blocked by Spamhaus?
If you receive the following message when attempting to sent an email to Avalara "Service unavailable; Client host [your IP Address] blocked using Spamhaus; To request removal from this list see http://www.spamhaus.org/lookup.lasso", it means that the Spamhaus spam blocking service has flagged your IP address as spam and is preventing it from being received. In order to correct this you will need to contact the Spamhaus address listed in the error to get removed from their block lists. You may also want to make sure that the email accounts in your organization are secure and not sending out spam.
You have been flagged as a spammer by the Spamhaus services.