回复：我用学校的网络，设置的OUTLOOK不能收发信笺了。

2 posibilities:
1) school firewall prevent you talking to external mail server.
2) school mail server does not allow you send/receive from email agent, to prevent email relay. Some time, they require you to estabilish a secured login channel first, for example, throught SSH Client.

You need to talk to your school admin to find out.