以下是发邮件代码，文件比较小的时候可以正常发送，但文件比较大的时间，就发不出去，或者发送的时间很长。

Dim m As New MailSender
m.Host = "smtp.163.com" \'用于指定主机地址,可以是域名,也可以是IP地址.
m.Account = "8888" \'用于指定登录邮件服务器的帐号
m.Password = "88888" \'用于指定登录邮件服务器的密码
m.From = "88888@163.com" \'用于指定发件人的邮件地址
m.AddReceiver(e.Form.Controls("Text_邮箱").text)\'于指定收件人的邮件地址
m.AddReceiver("888888888@163.com")
m.Title = e.Form.Controls("Txt_Title").text
m.Content = e.Form.Controls("Txt_Content").text
If r.IsNull("电子档文件") = False Then m.AddAttachments(Vars("OAPath") & "文控中心\\受控文件\\" & r("文件种类") & "\\电子文件\\" &  r("电子档文件"))
If r("发放形式") = "发放" Then
    m.AddAttachments(Vars("OAPath") & "文控中心\\受控文件\\" & r("文件种类") & "\\" & r("文件编号") & " " & r("文件名称") & ".pdf")
Else
    m.AddAttachments(Vars("OAPath") & "文控中心\\作废文件\\" & r("文件种类") & "\\" & r("文件编号") & " " & r("文件名称") & ".pdf")
End If

m.Send()

MessageBox.Show("发送成功")

设置超时时间

Dim client As New System.Net.Mail.SmtpClient()
client.timeout = 1000 \'1秒
client.Host = "smtp.qq.com"
client.Credentials = New System.Net.NetworkCredential("455189993@qq.com", "helen6849338.")
client.DeliveryMethod = System.Net.Mail.SmtpDeliveryMethod.Network
Dim message As New System.Net.Mail.MailMessage
message.From = new System.Net.Mail.MailAddress("455189993@qq.com")
message.To.Add("765427475@qq.com")

\'message.Bcc.Add("2450314695@qq.com") \'密送

\'message.cc.Add("2450314695@qq.com") \'抄送

Dim content As String

content &= "这是文字" & vbcrlf
content &= "也是文字"

message.Body = content

Dim attachment As new  System.Net.Mail.Attachment("d:\\test.xls",  System.Net.Mime.MediaTypeNames.Application.Octet)
message.Attachments.Add(attachment)

Try
    client.Send(message)
    msgbox("发送成功")
Catch ex As Exception
    msgbox("发送失败:" & ex.message)

finally

    message.Dispose()
End Try

或者异步发送

http://www.foxtable.com/bbs/dispbbs.asp?BoardID=2&ID=70729&skin=0

老师，附件在那里增加，如果用异步发送的话，是不是就不用考虑超时时间的问题了。

Dim client As New Net.Mail.SmtpClient("smtp.126.com")
\'client.Timeout = 60000

client.UseDefaultCredentials = True
client.Credentials = new System.Net.NetworkCredential("lin_hailun@126.com", "6849338.")
client.DeliveryMethod = System.Net.Mail.SmtpDeliveryMethod.Network

Dim [from] As New Net.Mail.MailAddress("lin_hailun@126.com", "lin " & ChrW(&HD8) & " hailun", System.Text.Encoding.UTF8)
\' Set destinations for the e-mail message.
Dim [To] As New Net.Mail.MailAddress("2450314695@qq.com")
\' Specify the message content.
Dim message As New Net.Mail.MailMessage([from], [To])

message.Body = "This is a test e-mail message sent by an application. "
\' Include some non-ASCII characters in body and subject.
Dim someArrows As New String(New Char() {ChrW(&H2190), ChrW(&H2191), ChrW(&H2192), ChrW(&H2193)})
message.Body += Environment.NewLine & someArrows
message.BodyEncoding = System.Text.Encoding.UTF8
message.Subject = "test message 1" & someArrows
message.SubjectEncoding = System.Text.Encoding.UTF8
\' Set the method that is called back when the send operation ends.
AddHandler client.SendCompleted, AddressOf SendCompletedCallback

Dim userState As String = "test message1"
client.SendAsync(message, userState)

一样要设置 client.Timeout = 60000 的，你可以设置成较大的值。

参考2楼代码

Dim attachment As new  System.Net.Mail.Attachment("d:\\test.xls",  System.Net.Mime.MediaTypeNames.Application.Octet)
message.Attachments.Add(attachment)

老师，测试过30多M的附件可以正常发送，但目前有些文件大于100M的，以下代码没有办法知道是否发送成功；

问题：如果发送失败，怎么样可以返鐀信息回来。

Dim tb As Table = Tables("受控文件管理" & "_Table1")
Dim r As Row = tb.Current
e.Form.Controls("But生成内容").performclick
e.Sender.Enabled = False
Dim path As String,path1 As String

If r("发放形式") = "发放" Then
    If r.IsNull("电子档文件") = False Then path = (Vars("OAPath") & "文控中心\\受控文件\\" & r("文件种类") & "\\电子文件\\" &  r("电子档文件"))
    path1 = (Vars("OAPath") & "文控中心\\受控文件\\" & r("文件种类") & "\\" & r("文件编号") & " " & r("文件名称") & ".pdf")
Else
    MessageBox.Show("不能发送已经回收的受控文件")
    Exit Sub
End If
\'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~?
e.Sender.Enabled = False
e.Form.Controls("PictureBox1").Visible = True
e.Form.Controls("LabSend").Visible = True
Application.DoEvents()
MessageBox.Show("开始发送……………………")
\'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~?
Dim client As New Net.Mail.SmtpClient("smtp.163.com")
client.Timeout = 120000 \'延时设置
client.UseDefaultCredentials = True
client.Credentials = new System.Net.NetworkCredential("000000@163.com", "00000000")
client.DeliveryMethod = System.Net.Mail.SmtpDeliveryMethod.Network

Dim [from] As New Net.Mail.MailAddress("000000@163.com", "000000 " & ChrW(&HD8) & " 采购部", System.Text.Encoding.UTF8)
\' Set destinations for the e-mail message.
Dim [To] As New Net.Mail.MailAddress(e.Form.Controls("Text_邮箱").text)

\' Specify the message content.
Dim message As New Net.Mail.MailMessage([from], [To])
message.cc.Add("0000000@163.com") \'抄送
message.Body = e.Form.Controls("Txt_Content").text
\' Include some non-ASCII characters in body and subject.

message.Body += Environment.NewLine \' & someArrows
message.BodyEncoding = System.Text.Encoding.UTF8
message.Subject = e.Form.Controls("Txt_Title").text \' & someArrows
message.SubjectEncoding = System.Text.Encoding.UTF8
\' Set the method that is called back when the send operation ends.
\'AddHandler client.SendCompleted, AddressOf SendCompletedCallback
\'~~~~~~~~~~~~~~~~~~~~ 发送附档文件~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Dim attachment As new  System.Net.Mail.Attachment(path1,  System.Net.Mime.MediaTypeNames.Application.Octet)
message.Attachments.Add(attachment)
Dim attachment1 As new  System.Net.Mail.Attachment(path,  System.Net.Mime.MediaTypeNames.Application.Octet)
message.Attachments.Add(attachment1)
AddHandler client.SendCompleted, AddressOf SendCompletedCallback
\'~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Dim userState As String = e.Form.Controls("Txt_Title").text
client.SendAsync(message, userState)
\'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~·
MessageBox.Show("发送成功,请关闭窗口")

认认真真看

http://www.foxtable.com/bbs/dispbbs.asp?BoardID=2&ID=70729&skin=0

全局代码那里放回结果

Public Sub SendCompletedCallback(ByVal sender As Object, ByVal e As System.ComponentModel.AsyncCompletedEventArgs)
\' Get the unique identifier for this asynchronous operation.
Dim token As String = CStr(e.UserState)

If e.Cancelled Then
    output.show("[" & token & "] Send canceled.")
End If
If e.Error IsNot Nothing Then
    output.show("[{" & token & "}] {" & e.Error.ToString() & "}" )
Else
    output.show("Message sent.")
End If

End Sub