
Check for more information on compacting folders. * Do you regularly compact your folders? Weekly or more often is strongly recommended. * Are you using an antivirus and/or a firewall program? Which ones? * Is your mail service from an ISP, corporate e-mail system or Web-based? * What is the exact wording of the error message you are receiving? * Which version of Thunderbird? Check Help>About for the version number. When posting to a forum to request support it is helpful to detail what has already been tried so that folks won't post suggestions for the same unsuccessful "solutions". Um, you really need to give us more information.


Check that you have all your Mail settings correct.
