Jmail接收邮件及UTF-8解码问题，含VB及C#代码

2023-06-15 22:12•linux•阅读 3694

Jmail接收到的邮件，如果标题的编码方式是UTF-8的话，直接从Base64解码出来的话中文会出现乱码(英文正常)，这就导致用Jmail组件收发邮件时有些邮箱的正常，有些邮箱乱码，不够完善。

例如：

QQ邮箱：

　　Subject: =?gbk?B?1rG907T4uL28/reiy80=?=

U-Mail邮箱

　　 Subject: =?utf-8?B?5oiR5b6X57uZ5oiR?=

正是因为前几天帮同学弄Jmail收邮件的时候碰到此类问题，所以从网上收集了一些这方面的一些资源，希望能让大家少走点弯路！

Jmail的subject共分3段，=?和?=是结束和结尾标记

第一段：utf-8，原来页面的编码方式

第二段：B是指邮件的编码方式B就是base64

第三段：5oiR5b6X57uZ5oiR标题的内容，但是经过Base64编码了

所以出现了QQ邮箱收邮件正常，而收取U-Mail中的邮件时标题乱码的现象，本质就是U-mail用到的是UTF-8编码

看到了本质要解决Jmail收件标题乱码就很简单了。只要获取subject第3个问号和第4个问号间的内容进行base64解码即可。

VB部分：

Option Explicit

Dim i&, Attachment&

Dim att As Object

Dim EmailMsg As Object

Dim atts As Object

Dim JMail As Object

Dim EmailList$, Subject$, EmailID&

Dim X$()

Private Sub Command1_Click()

Dim J#

Set JMail = CreateObject("JMail.POP3")

JMail.Connect "***@163.com", "***", "pop.163.com", "110" 'JMail.Connect "邮箱名", "密码", "服务器" [,"端口号"]

' Debug.Print "你有" & JMail.Count & "封邮件" '邮件数量

For i = 1 To JMail.Count

' EmailID = JMail.GetMessageUID(I) '邮件唯一ID标识

Set EmailMsg = JMail.Messages.Item(i) '取得一条邮件信息

'-----------------------------------------------------------------------------取得附件数量并下载

Set atts = EmailMsg.Attachments '附件集合

Attachment = atts.Count '附件的数量

If Attachment > 0 Then

For J = 0 To Attachment - 1

Set att = atts(J)

If Dir(App.Path & "\" & att.Name) = "" Then 'att.Name附件的名称，如果存在同名文件而不加判断则会出错

att.SaveToFile App.Path & "\" & att.Name

End If

Next J

End If

'------------------------------------------------------------------------------以下为各种参数设置

' EmailMsg.Charset = "gb2312" '编码方式

' EmailMsg.ContentTransferEncoding = "base64"'解码方式

' EmailMsg.Encoding = "base64"

' EmailMsg.ContentType = "multipart/mixed" '发送邮件时

' EmailMsg.ContentType = "text/html" '接收邮件时

' EmailMsg.ISOEncodeHeaders = False'True '功能不清？

'-----------------------------------------------------------------------------可以取得的各元素

' MsgBox EmailMsg.Priority '邮件的优先级，1-5，1最高，正常情况为3。

' MsgBox EmailMsg.From '邮件的发送人的信箱地址

' MsgBox EmailMsg.FromName '邮件的发送人

' MsgBox EmailMsg.Date '邮件日期

' MsgBox EmailMsg.Body '邮件内容

' MsgBox EmailMsg.Size '邮件大小

'----------------------------------------------------------------------------

Subject = EmailMsg.Headers.GetHeader("Subject") '邮件标题，可正常解码，但UTF-8格式的标题取不全

X = Split(EmailMsg.Headers.GetHeader("Subject"), "?")

If X(1) = "UTF-8" Then

Subject = Utf8ToUnicode(StrToBytes(X(3)))

Else

Subject = Base64Decode(X(3))

End If

' Subject = EmailMsg.Headers.GetHeader("From") '发件人，可解码

' Subject = EmailMsg.Headers.GetHeader("FromName")

EmailList = EmailList & CStr(i) & "、" & Subject & vbCrLf

DoEvents

Text1.Text = EmailList

End Sub

Base64.bas模块：

Option Explicit

Public Const cstBase64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"

Public arrBase64() As String

Private Declare Function MultiByteToWideChar Lib "kernel32" (ByVal CodePage As Long, ByVal dwFlags As Long, ByVal lpMultiByteStr As Long, ByVal cchMultiByte As Long, ByVal lpWideCharStr As Long, ByVal cchWideChar As Long) As Long

Private Declare Function WideCharToMultiByte Lib "kernel32" (ByVal CodePage As Long, ByVal dwFlags As Long, ByVal lpWideCharStr As Long, ByVal cchWideChar As Long, ByVal lpMultiByteStr As Long, ByVal cchMultiByte As Long, ByVal lpDefaultChar As Long, ByVal lpUsedDefaultChar As Long) As Long

Private Const CP_ACP = 0 ' default to ANSI code page

Private Const CP_UTF8 = 65001 ' default to UTF-8 code page

Public Function Base64Encode(strSource As String) As String '编码

On Error Resume Next

If UBound(arrBase64) = -1 Then

arrBase64 = Split(StrConv(cstBase64, vbUnicode), vbNullChar)

End If

Dim arrB() As Byte, bTmp(2) As Byte, bT As Byte

Dim i As Long, J As Long

arrB = StrConv(strSource, vbFromUnicode)

J = UBound(arrB)

For i = 0 To J Step 3

Erase bTmp

bTmp(0) = arrB(i + 0)

bTmp(1) = arrB(i + 1)

bTmp(2) = arrB(i + 2)

bT = (bTmp(0) And 252) / 4

Base64Encode = Base64Encode & arrBase64(bT)

bT = (bTmp(0) And 3) * 16

bT = bT + bTmp(1) \ 16

Base64Encode = Base64Encode & arrBase64(bT)

bT = (bTmp(1) And 15) * 4

bT = bT + bTmp(2) \ 64

If i + 1 <= J Then

Base64Encode = Base64Encode & arrBase64(bT)

Else

Base64Encode = Base64Encode & "="

End If

bT = bTmp(2) And 63

If i + 2 <= J Then

Base64Encode = Base64Encode & arrBase64(bT)

Else

Base64Encode = Base64Encode & "="

End If

End Function

Public Function Base64Decode(strEncoded As String) As String '解码

On Error Resume Next

Dim arrB() As Byte, bTmp(3) As Byte, bT As Long, bRet() As Byte

Dim i As Long, J As Long

arrB = StrConv(strEncoded, vbFromUnicode)

J = InStr(strEncoded & "=", "=") - 2

ReDim bRet(J - J \ 4 - 1)

For i = 0 To J Step 4

Erase bTmp

bTmp(0) = (InStr(cstBase64, Chr(arrB(i))) - 1) And 63

bTmp(1) = (InStr(cstBase64, Chr(arrB(i + 1))) - 1) And 63

bTmp(2) = (InStr(cstBase64, Chr(arrB(i + 2))) - 1) And 63

bTmp(3) = (InStr(cstBase64, Chr(arrB(i + 3))) - 1) And 63

bT = bTmp(0) * 2 ^ 18 + bTmp(1) * 2 ^ 12 + bTmp(2) * 2 ^ 6 + bTmp(3)

bRet((i \ 4) * 3) = bT \ 65536

bRet((i \ 4) * 3 + 1) = (bT And 65280) \ 256

bRet((i \ 4) * 3 + 2) = bT And 255

Base64Decode = StrConv(bRet, vbUnicode)

End Function

Function StrToBytes(ByVal Source As String) As Byte()

Dim bB64Str() As Byte

bB64Str = StrConv(Source, vbFromUnicode)

Dim lB64Len As Long

lB64Len = InStrB(bB64Str, ChrB$(Asc("="))) - 1

Dim lLenPad As Long

lLenPad = (4 - lB64Len Mod 4) Mod 4

Dim lLen As Long

lLen = ((lB64Len + lLenPad) \ 4) * 3

Dim bStr() As Byte

ReDim bStr(lLen - 1)

lLen = lLen - lLenPad

Dim i As Long

Dim lBuffer As Long

For i = 0 To lB64Len - 1 Step 4

lBuffer = DeB64CodeA(bB64Str(i + 0)) * &H40000 Or DeB64CodeA(bB64Str(i + 1)) * &H1000& _

Or DeB64CodeA(bB64Str(i + 2)) * &H40& Or DeB64CodeA(bB64Str(i + 3))

bStr((i \ 4) * 3 + 2) = lBuffer And &HFF&

lBuffer = lBuffer \ &H100&

bStr((i \ 4) * 3 + 1) = lBuffer And &HFF&

lBuffer = lBuffer \ &H100&

bStr((i \ 4) * 3 + 0) = lBuffer And &HFF&

lBuffer = lBuffer \ &H100&

ReDim Preserve bStr(lLen - 1)

StrToBytes = bStr

End Function

Private Function DeB64CodeA(ByVal Char As Byte) As Byte

Select Case Char

Case Asc("A") To Asc("Z"): DeB64CodeA = Char - Asc("A")

Case Asc("a") To Asc("z"): DeB64CodeA = Char - Asc("a") + 26

Case Asc("0") To Asc("9"): DeB64CodeA = Char - Asc("0") + 52

Case Asc("+"): DeB64CodeA = 62

Case Asc("/"): DeB64CodeA = 63

Case Asc("="): DeB64CodeA = 64

End Select

End Function

Function Utf8ToUnicode(ByRef Utf() As Byte) As String

Dim lRet As Long

Dim lLength As Long

Dim lBufferSize As Long

lLength = UBound(Utf) - LBound(Utf) + 1

If lLength <= 0 Then Exit Function

lBufferSize = lLength * 2

Utf8ToUnicode = String$(lBufferSize, Chr(0))

lRet = MultiByteToWideChar(CP_UTF8, 0, VarPtr(Utf(0)), lLength, StrPtr(Utf8ToUnicode), lBufferSize)

If lRet <> 0 Then

Utf8ToUnicode = Left(Utf8ToUnicode, lRet)

End If

End Function

C#部分：

#region base64解码

public static string base64GbkDecode(string data)

{

string decode = "";

byte[] bytes = Convert.FromBase64String(data);

try

{

decode = Encoding.GetEncoding("gb2312").GetString(bytes);

}

catch (Exception ex1)

{

//return "Error in base64Encode" + ex1.Message;

}

return decode;

}

public static string base64Utf8Decode(string data)

{

string result = "";

try

{

System.Text.UTF8Encoding encoder = new System.Text.UTF8Encoding();

System.Text.Decoder utf8Decode = encoder.GetDecoder();

byte[] todecode_byte = Convert.FromBase64String(data);

int charCount = utf8Decode.GetCharCount(todecode_byte, 0, todecode_byte.Length);

char[] decoded_char = new char[charCount];

utf8Decode.GetChars(todecode_byte, 0, todecode_byte.Length, decoded_char, 0);

result = new String(decoded_char);

}

catch (Exception e)

{

//return "Error in base64Encode" + e.Message;

}

return result;

}

//base64解码

public static string DecodeStr(string allstr, string code)

{

//形如=?...?=是结束开始的标志

//=?utf-8?B?5rWL6K+V5o6l5pS25pys6YKu5Lu26L+Z5piv5Li76aKY?=

//=?gbk?B?suLK1L3TytXN4rK/08q8/tXiuPbKx9b3zOU=?=

//返回的字符串

string str = "";

if (code == "gbk")

{

str = base64GbkDecode(allstr);

}

else if (code == "utf-8")

{

str = base64Utf8Decode(allstr);

}

return str;

}

#endregion

调用：

string subjectStr = popMail.Messages[i].Headers.GetHeader("Subject");

subjectstr = DecodeStr(subjectallstr.Split('?')[3], “utf-8”);

注意：如果原来页面用的是UTF-8编码，一定要用popMail.Messages[i].Headers.GetHeader(“Subject”)的形式，popMail.Messages[i].Subject得到的将是直接经jmail解码后的乱码

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Jmail接收邮件及UTF-8解码问题，含VB及C#代码

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