I have a message filter setup that forwards incoming emails with certain words in the subject line to two other email accounts. When the filter activates, I get an error message which according to the Google searches I've made suggests that Thunderbird is trying to forward the emails too quickly and is overrunning to outbound server queue. An image of the error message is attached but the main detail is copied here. An error occurred while sending email. The mail server responded: 432 4.3.2 STOREDRV.ClientSubmit; sender thread limit exceeded [Hostname=BYAPR06MB5286.namprd06.prod.outlook.com]. Please check message and try again. I have broken the current action that forwards the incoming email to two email accounts into two separate actions each forwarding the email to one account but the error message still appears. I'm thinking of adding additional actions between the two I have now that will add more time between the forwarding actions. I'm thinking of setting the priority to normal or something equally harmless just to introduce a delay between the forwarding actions. Any ideas from the community on this would be appreciated.