January 6, 2004 Dave Wanta has created an
entire Web site devoted to using the System.Web.Mail namespace. Check it out! -------------------------------------------------------------------------------------------
4 January 2004THIS THREAD IS LOCKED. If you have a question about sending email with ASP.NET, please start a new thread in the
Getting Started forum (or other forum, as appropriate). Thanks! -------------------------------------------------------------------------------------------
22 Aug 2003 Added link to page on how SMTP works 14 October 2003 Added information on passing authentication credentials with the message
14 October 2003 Added a note on how to add a Reply-To. Hello, everyone. I've assembled below a list of the most common issues I've seen (and experienced) with sending email from ASP.NET applications. Sorry about the length of the list, but I wanted to
get into it all the stuff I had accumulated. I split it into two parts -- configuration and troubleshooting. If you know of other issues, please add to the thread! Thanks, -- Mike ==========================================================
I. FORMATTING AND SENDING EMAIL MESSAGES * What do I need in order to be able to send email from an ASP.NET application? * How do I configure a local SMTP server? * What should I specify for the SmtpServer property? * Can I specify multiple recipients
for a message? * Can I use a "friendly name" in the To and From properties? * How do I add an attachment to an email? * Can I specify authentication information as part of the email message in ASP.NET? * How do I add a Reply-To field?
What do I need in order to be able to send email from an ASP.NET application? 1) Access to an SMTP server that can relay your message to the recipient's email server. See "How do I configure a local SMTP server?" and "What should I specify for the SmtpServer
property?". 2) The CDOSYS.dll file (Collaboration Data Objects), which should be in your Windows\System folder. The CDOSYS.dll file is part of Windows XP and Windows 2003. In some earlier versions of Windows it was not available, but would be installed as
part of Microsoft Office. 3) Code such as the following:
Dim mailMessage As System.Web.Mail.MailMessage
mailMessage = New System.Web.Mail.MailMessage
mailMessage.From = "me@contoso.com "
mailMessage.To = "you@contoso.com "
mailMessage.Subject = "Test subject"
mailMessage.BodyFormat = System.Web.Mail.MailFormat.Text
mailMessage.Body = "Testing email "
System.Web.Mail.SmtpMail.SmtpServer = "localhost"
Try
System.Web.Mail.SmtpMail.Send(mailMessage)
Label1.Text = "Message sent!"
Catch ex As Exception
Label1.Text = ex.Message
End Try
How do I configure a local SMTP server?
Install the SMTP virtual server that is part of IIS. You will need your Windows installation CD. Use Add or Remove Programs in the Windows Control Panel to launch Add/Remove Windows Components. Select Internet Information Services (IIS) and then click Details. Check SMTP Service and then click OK. The installation process will prompt you for your Windows CD and will install the SMTP virtual server.
After installing the SMTP server (and possibly rebooting), configure it by following these steps:
1) In the Control Panel, choose Administrative Tools, and then choose Internet Information Services.
2) Open the node for your computer, right-click the Default SMTP Virtual Server node and choose Properties.
3) In the Access tab, click Connection.
4) Select Only the list below, click Add and add the IP 127.0.0.1. This restricts connections to just the local computer, i.e., localhost. Close the Connection dialog box.
5) Click Relay and repeat Step 5 to allow only localhost to relay through this server.
In your firewall or router (or both), close incoming port 25. This is an important security measure that will prevent spammers from finding your SMTP server and using it to relay spam.
For troubleshooting, you might want to turn on logging. In the General tab, check Enable logging. See the section below on troubleshooting.
What should I specify for the SmtpServer property?
1) If you have IIS configured as an SMTP virtual server, specify "localhost." If you are on a LAN, you might not be allowed to use a local server; see next point.
2) If you are on a local area network with a dedicated SMTP server, use the name of that server. (Sometimes this is a server named "smarthost.") Check with your network administrator.
3) If the SMTP server is on another computer, specify the IP address of that computer. The remote SMTP server must be configured a) to accept incoming relay requests through port 25, and b) to allow your computer to connect to it, and c) to allow your computer to relay email messages. Note: Configuring a remote server to allow connections from other computers can be a security issue, since it might allow spammers to connect to the server!
4) If you are a home user, you might be able to relay email through your ISP. You can try specifying the mail server name. (In Outlook, look under Tools > Accounts > Properties > Servers > Outgoing Mail (SMTP)).
Can I specify multiple recipients for a message?
Yes. Delimit each recipient with a semicolor (;) in the mailMessage.To property:
Can I use a "friendly name" in the To and From properties?
Yes. Format the email address this way:
mailMessage.From = "Name "
How do I add an attachment to an email?
Create a MailAttachment object and add it to the Attachments collection of the email message:
Dim emailMessage As New MailMessage
emailMessage.From = textSenderEmail.Text
emailMessage.To = "you@contoso.com"
emailMessage.Subject = "me@contoso.com"
emailMessage.Body = "Sample message
Dim path As String
path = Server.MapPath(Request.ApplicationPath & "\images\")
Dim slideUrl As String = "vacationslide1.jpg"
Dim emailAttach As New MailAttachment(path & slideUrl)
emailMessage.Attachments.Add(emailAttach)
SmtpMail.SmtpServer="localhost"
Can I specify authentication information as part of the email message in ASP.NET?
If you are using version 1.0 of the .NET Framework, no. However, in version 1.1, support was added for CDO fields (see this MSDN topic for information on CDO fields). mharder posted an example of passing credentials using Basic authentication in this post: 274406.
How do I add a Reply-To field?
A Reply-To field is the address to which any replies will be sent. This is used when you want replies to be directed to someone other than the address in the From property. To set Reply-To, use this syntax:
(Thanks to Colt Kwong for this tip!)
====================
II. TROUBLESHOOTING
* How can I determine if my email is being sent successfully?
* Can I log status messages and errors? Updated 22 Aug 2003
* What does error message xxxx mean?
* Why does my email go through to some recipients but not others?
How can I determine if my email is being sent successfully?
You have limited ways (in code) to determine the success of sending email. Sending email is a loosely coupled process. When you call the MailMessage.Send method, ASP.NET invokes the CDO code to write a properly formatted SMTP message to the outgoing queue of the specified server. You can wrap the Send method in a Try-Catch block, but this tells you only that the message was successfully queued.
If the SMTP server is able to relay the message but the recipient's email address is invalid, a delivery status notification email message is sent to the From address on the message. If the domain name cannot be found (for example, "aninvalidname@atotallyinvaliddomain.com"), you will get an error from your SMTP server (for example, from postmaster@computername). If the domain name is valid but the recipient does not exist (for example, "aninvalidname@microsoft.com"), the email server at the target domain generally sends an error email message to the From address. In that case, you might not know for some time that the email you sent did not reach a recipient.
For various reasons the SMTP server might not be able to relay the message at all. You can check the status of outgoing email in two ways:
* Examine the queue. If you are using a local SMTP server, the outgoing email messages are queued in \Inetpub\mailroot\queue as files with an .eml extension. The SMTP server periodically looks for messages in the queue folder and sends them. If a message appears to be stuck in the queue, there is a problem in sending it. You might try copying it to a different folder or just deleting it.
Tip If messages are piling up, you might be able to clear the queue by stopping and restarting the SMTP server.
* Examine the log. See next question.
Can I log status messages and errors?
Yes, if you are using a local SMTP server. (If you are using a different SMTP server, check with the server administrator.) To enable logging:
1) In the Control Panel, choose Administrative Tools, and then choose Internet Information Services.
2) Open the node for your computer, right-click the Default SMTP Virtual Server node, and then choose Properties.
3) In the General tab, check Enable logging.
4) Optionally, set the log file format. Click Advanced to change how often the log file is written to disk and to set other options.
To examine the log, open the log folder (by default, \WINDOWS\system32\Logfiles\SMTPSVC1) and open the log entries with a text editor. A successful sequence of events for an email message will look something like this:
If there is a problem sending a message, the log will (might) contain the text of an error message associated with the entry. The message might have a plus sign (+) in place of spaces.
UpdateThis page has a good description of how the client and server talk to one another, including explanations for the somewhat cryptic codes in the log. I got this information via a link on Charles Miller's
blog. What does error message xxxx mean? The error messages for sending email are unfortunately not very helpful. The following list shows some SMTP errors that can result from calling the Send method, and
possible explanations. The transport failed to connect to the server 1) The server specified in the SmtpServer property is not valid. 2) The SMTP server requires authentication to relay email. The ASP.NET mail classes do not allow you to include authentication
information. If you are working with a local SMTP server, you might be able to configure the server so that it does not require authentication for a local relay (127.0.0.1).
Could not access 'CDO.Message' object. 1) The mail message does not have a valid To or From property value. The email addresses you specify must be well-formed. See also "Can I use a "friendly name" in the To and From properties?" above. 2) The server
specified in the SmtpServer property is not valid or not available. The SendUsing configuration value is invalid. A recent security update can cause this error. See KnowledgeBase article 324037. (http://support.microsoft.com/default.aspx?scid=kb%3Ben-us%3B324037).
550 5.7.1 Unable to relay for xxxxx or 550 not local host xxxxx, not a gateway The SMTP server is not configured to allow you to relay. If you are working with a local SMTP server, you can configure it to allow relaying for IP 127.0.0.1.
Why does my email go through to some recipients but not others? If you are a home user, your ISP might assign you a dynamic IP. As an anti-spam measure, some recipients, such as AOL, refuse email that is sent from a dynamic IP. Check the SMTP log to
see if you can get details about why a message cannot be sent. If recipients are rejecting email from your local SMTP server, you
might be able to relay through your ISP's mail server. See "What should I specify for the SmtpServer property?" above.
mikepope
Contributor
5803 Points
1155 Posts
Microsoft
SMTP server and email FAQ
Jul 04, 2003 05:36 PM|LINK
emailMessage.Headers.Add("Reply-To", "name@contoso.com")(Thanks to Colt Kwong for this tip!) ==================== II. TROUBLESHOOTING * How can I determine if my email is being sent successfully? * Can I log status messages and errors? Updated 22 Aug 2003 * What does error message xxxx mean? * Why does my email go through to some recipients but not others? How can I determine if my email is being sent successfully? You have limited ways (in code) to determine the success of sending email. Sending email is a loosely coupled process. When you call the MailMessage.Send method, ASP.NET invokes the CDO code to write a properly formatted SMTP message to the outgoing queue of the specified server. You can wrap the Send method in a Try-Catch block, but this tells you only that the message was successfully queued. If the SMTP server is able to relay the message but the recipient's email address is invalid, a delivery status notification email message is sent to the From address on the message. If the domain name cannot be found (for example, "aninvalidname@atotallyinvaliddomain.com"), you will get an error from your SMTP server (for example, from postmaster@computername). If the domain name is valid but the recipient does not exist (for example, "aninvalidname@microsoft.com"), the email server at the target domain generally sends an error email message to the From address. In that case, you might not know for some time that the email you sent did not reach a recipient. For various reasons the SMTP server might not be able to relay the message at all. You can check the status of outgoing email in two ways: * Examine the queue. If you are using a local SMTP server, the outgoing email messages are queued in \Inetpub\mailroot\queue as files with an .eml extension. The SMTP server periodically looks for messages in the queue folder and sends them. If a message appears to be stuck in the queue, there is a problem in sending it. You might try copying it to a different folder or just deleting it. Tip If messages are piling up, you might be able to clear the queue by stopping and restarting the SMTP server. * Examine the log. See next question. Can I log status messages and errors? Yes, if you are using a local SMTP server. (If you are using a different SMTP server, check with the server administrator.) To enable logging: 1) In the Control Panel, choose Administrative Tools, and then choose Internet Information Services. 2) Open the node for your computer, right-click the Default SMTP Virtual Server node, and then choose Properties. 3) In the General tab, check Enable logging. 4) Optionally, set the log file format. Click Advanced to change how often the log file is written to disk and to set other options. To examine the log, open the log folder (by default, \WINDOWS\system32\Logfiles\SMTPSVC1) and open the log entries with a text editor. A successful sequence of events for an email message will look something like this: If there is a problem sending a message, the log will (might) contain the text of an error message associated with the entry. The message might have a plus sign (+) in place of spaces. Update This page has a good description of how the client and server talk to one another, including explanations for the somewhat cryptic codes in the log. I got this information via a link on Charles Miller's blog. What does error message xxxx mean? The error messages for sending email are unfortunately not very helpful. The following list shows some SMTP errors that can result from calling the Send method, and possible explanations. The transport failed to connect to the server 1) The server specified in the SmtpServer property is not valid. 2) The SMTP server requires authentication to relay email. The ASP.NET mail classes do not allow you to include authentication information. If you are working with a local SMTP server, you might be able to configure the server so that it does not require authentication for a local relay (127.0.0.1). Could not access 'CDO.Message' object. 1) The mail message does not have a valid To or From property value. The email addresses you specify must be well-formed. See also "Can I use a "friendly name" in the To and From properties?" above. 2) The server specified in the SmtpServer property is not valid or not available. The SendUsing configuration value is invalid. A recent security update can cause this error. See KnowledgeBase article 324037. (http://support.microsoft.com/default.aspx?scid=kb%3Ben-us%3B324037). 550 5.7.1 Unable to relay for xxxxx or 550 not local host xxxxx, not a gateway The SMTP server is not configured to allow you to relay. If you are working with a local SMTP server, you can configure it to allow relaying for IP 127.0.0.1. Why does my email go through to some recipients but not others? If you are a home user, your ISP might assign you a dynamic IP. As an anti-spam measure, some recipients, such as AOL, refuse email that is sent from a dynamic IP. Check the SMTP log to see if you can get details about why a message cannot be sent. If recipients are rejecting email from your local SMTP server, you might be able to relay through your ISP's mail server. See "What should I specify for the SmtpServer property?" above.