对于一封邮件进入数据库后的存放位置很困惑 ，我的理解入下表，打问号的地方是我困惑的 ，请各位指教！！
A,B,D,H 为同一个域中的用户，A,B采用EXCHANGE的连接方式，D,H采用远程连接方式，E 为外部邮箱，例如SINA
| outlook(A,B),POP3(D,H),Internet(E),Domain(A,B,D,H) | | |
| | | |
| A->B(2M) | A send | MAPI
| 4M saved in EDB |
| B receive | MAPI
| 2M download from EDB |
| A->D(2M) | A send | MAPI
| 4M saved in EDB |
| D receive | POP3 | 2M download EDB,Conversion(mapi to stm) |
| A->E(2M) | A send | MAPI
| 2M download from EDB |
| | |
| | | |
| D->A(2M) | D send | SMTP | 2M saved in STM? |
| A receive | MAPI | |
| D->E(2M) | D send | SMTP | 2M saved in STM? |
| | |
| D->H(2M) | D send | SMTP | 4M saved in STM |
| H receive | POP3 | 2M download from STM,NO Conversion |
| | | |
| E->A(2M) | E send | SMTP | 2M saved in STM |
| A receive | MAPI | 2M download from STM,Conversion(stm to mapi) |
| E->D(2M) | E send | SMTP | 2M saved in STM |
| D receive | POP3 | 2M download from STM,NO Conversion |
