看退信下面的日志，并按照相應的錯誤信息進行匹配。

511 sorry, no mailbox here by that name

unknown user account

... User unknown

Name server reports domain name unknown

mailbox unavailable

550 Invalid User:

invalid recipient

No such user here

All recipients are invalid

User unknown in virtual alias table

Mailbox not found

Recipient address rejected: User unknown in relay recipient table

以上信息均為收件人地址錯誤或者無效，檢查收件人地址，檢查郵件服務器的域名解析服務器

554 Connection refused(mx). MAIL FROM [test@test.com] mismatches client IP [74.86.11.12].

域名和IP 地址不對應導致的拒收 [上面的域名和IP 地址會變化，類似的情況]，修正您的域名解析，域名解析請參考：http://www.6677111.com/windows/install/954.html

553 5.7.1 SpamTrap=reject mode, dsn=5.7.1, Message blocked by BOX Solutions (www.box-sol.com)

SpamTrap Technology, please contact the MUSTEK site manager for help: (bkndr63272).

如果出現(xiàn)類似上述的信息是因為您發(fā)了不受對方歡迎的信件，導致對方拒收

551 User not local; please try

郵件被GFW 過濾，GFW 是指Great Firewall，中國國家防火墻。嘗試將郵件內容打包壓縮或者放入OFFICE 文檔內進行郵件傳輸

Winsock Error 10053 Connection abort.

網(wǎng)絡通訊故障

Winsock Error 10060 The connection timed out.

連接超時，網(wǎng)絡通訊故障造成

Winsock Error 10061 The connection timed out.

對方服務器拒絕連接，對方服務器主動斷開鏈接，這通常是由國外不活躍的服務器造成的。

452 4.3.1 Out of memory

This message is 60 minutes old; it has 0 minutes left in this queue

Remote queue lifetime exceeded; message placed in retry queue

一般情況下，郵件會進入重試隊列進行再次發(fā)送，這種情況下對方的郵件服務器一般是Exchange，這是Exchange 的內部錯誤造成的。

553 Requested action not taken: no smtp MX

收件人郵箱地址錯誤，域名無法被解析,檢查收件人地址，或者對方域名解析設置錯誤。

501 syntax.helo hostname

501 Invalid domain name

502 unimplemented command

503 5.0.0 polite people say HELO first

533 relay restriction

544 <>:Recipient address rejected: Relay access denied

傳輸中的語法錯誤，原因不明。