Hi, I am using Thunderbird on Mac. When I start the application, everything works fine for like 5 minutes (sending and receiving e-mails), but after that, when I want to send an e-mail, it sends it but it is unable to put copy on the server. After that, Thunderbird looks like it is disconnected from the servers, because it even stops receiving e-mails. I just turn the app off and on again, and everything works just fine, but only after I send one or two e-mails, it starts showing it is unable to save a copy of the Sent e-mail again and disconects again. And also it is just doing when I am at work, at home everything works just fine. Do you know what it might be? Maybe something to do with static vs dynamic IP address? Thank you for you help in advance. Regards, Jiri