Sending an Email in C# with or without attachments: generic routine.

These are the same classes in VB.NET in case needed. I've also made the mail server address a parameter to allow the code to be runnable on copy paste. The problem while sending the bigger files was the smtp client's timeout(default 100s). I've made this dependent on the attachments' size allowing higher timeouts for bigger files.

Imports System.Text
Imports System.Net.Mail
Public Class SMTPMailSender
    ''' <summary>
    ''' Sends and email
    ''' </summary>
    ''' <param name="to">Message to address</param>
    ''' <param name="body">Text of message to send</param>
    ''' <param name="subject">Subject line of message</param>
    ''' <param name="fromAddress">Message from address</param>
    ''' <param name="fromDisplay">Display name for "message from address"</param>
    ''' <param name="credentialUser">User whose credentials are used for message send</param>
    ''' <param name="credentialPassword">User password used for message send</param>
    ''' <param name="attachments">Optional attachments for message</param>
    Public Shared Sub Email(ByVal mailServerAddress As String, ByVal [to] As String, ByVal body As String, ByVal subject As String, ByVal fromAddress As String, ByVal fromDisplay As String, ByVal credentialUser As String, ByVal credentialPassword As String, ByVal attachments() As MailAttachment)
        Dim host As String = mailServerAddress
        body = UpgradeEmailFormat(body) '  This  method is not completely implemented
        Try
            Dim mail As MailMessage = New MailMessage()
            mail.Body = body
            mail.IsBodyHtml = True
            mail.To.Add(New MailAddress([to]))
            mail.From = New MailAddress(fromAddress, fromDisplay, Encoding.UTF8)
            mail.Subject = subject
            mail.SubjectEncoding = Encoding.UTF8
            mail.Priority = MailPriority.Normal
            For Each ma As MailAttachment In attachments
                mail.Attachments.Add(ma.File)
            Next
            Dim Smtp As SmtpClient = New SmtpClient
            Smtp.EnableSsl = True ' This is necessary for gmail
            Smtp.Credentials = New System.Net.NetworkCredential(credentialUser, credentialPassword)
            Smtp.Host = host
            ' I am taking 1024th of the filesize in bytes and aggregating them. This gives me an ok value to deal with in sec (x1000 for ms) subject to a minimum of 100s.
             Smtp.Timeout = Math.Max(attachments.Sum(Function(Item) (DirectCast(Item, MailAttachment).Size / 1024)), 100) * 1000
            Smtp.Send(mail)
        Catch
            Dim sb As New StringBuilder(1024)
            sb.Append("\nTo:" + [to])
            sb.Append("\nbody:" + body)
            sb.Append("\nsubject:" + subject)
            sb.Append("\nfromAddress:" + fromAddress)
            sb.Append("\nfromDisplay:" + fromDisplay)
            sb.Append("\ncredentialUser:" + credentialUser)
            sb.Append("\ncredentialPasswordto:" + credentialPassword)
            sb.Append("\nHosting:" + host)
            Debug.Print(sb.ToString)
        End Try
    End Sub
    Private Shared Function UpgradeEmailFormat(ByVal body As String) As String
        ' This has to be implemented as needed. Currently doing nothing!
        Return body
    End Function
End Class

The MailAttachment Class has a new property size that is used to determine the attachment data length:

Imports System.IO
Imports System.Net.Mail
Imports System.Net.Mime
Public Class MailAttachment

    Private _stream As MemoryStream
    ''' <summary>
    ''' The data memory stream to use
    ''' </summary>
    Public Property Stream() As MemoryStream
        Get
            Return _stream
        End Get
        Set(ByVal value As MemoryStream)
            _stream = value
        End Set
    End Property
    Private _filename As String
    ''' <summary>
    ''' Gets the original filename for this attachment
    ''' </summary>
    Public Property Filename() As String
        Get
            Return _filename
        End Get
        Set(ByVal value As String)
            _filename = value
        End Set
    End Property
    Private _mediaType As String
    ''' <summary>
    ''' Gets the attachment type: Bytes or String
    ''' </summary>
    Public Property MediaType() As String
        Get
            Return _mediaType
        End Get
        Set(ByVal value As String)
            _mediaType = value
        End Set
    End Property
    ''' <summary>
    ''' Gets the file for this attachment (as a new attachment)
    ''' </summary>
    Public ReadOnly Property File() As Attachment
        Get
            Return New Attachment(Stream, Filename, MediaType)
        End Get
    End Property
    ''' <summary>
    ''' Gets the length of this attachement data
    ''' </summary>
    Public ReadOnly Property Size() As Double
        Get
            Return Me.Stream.Length
        End Get
    End Property
    ''' <summary>
    ''' Construct a mail attachment form a byte array
    ''' </summary>
    ''' <param name="data">Bytes to attach as a file</param>
    ''' <param name="filename">Logical filename for attachment</param>
    Public Sub New(ByVal data() As Byte, ByVal filename As String)
        Me.Stream = New MemoryStream(data)
        Me.Filename = filename
        Me.MediaType = MediaTypeNames.Application.Octet
    End Sub
    ''' <summary>
    ''' Construct a mail attachment from a string
    ''' </summary>
    ''' <param name="data">String to attach as a file</param>
    ''' <param name="filename">Logical filename for attachment</param>
    Public Sub New(ByVal data As String, ByVal filename As String)
        Me.Stream = New MemoryStream(System.Text.Encoding.ASCII.GetBytes(data))
        Me.Filename = filename
        Me.MediaType = MediaTypeNames.Text.Html
    End Sub
End Class