I have just moved a customer's Classic ASP website to their own VPS server (Windows 2003, 32-bit, IIS6, Virtual SMTP server) and after about 12 hours the website starting failing whenever it tried to send emails (CDO.Message).
Any script that sent an email took a very long time before it returned the error: Active Server Pages, ASP 0113, Script timed out. The standard timeout is in place. Strangely the custom error page which sends errors to me using the same email send method and settings (same function actually) was able to send me the error notification.
I needed to get the website going so I stopped/started the SMTP server which didn't help, then restarted IIS which resolved the issue immediately.
I am worried this might happen again. Any suggestions for what can cause this problem or does the default SMTP server need some additional settings to cope with a reasonably high-volume website?
Since classic ASP code has to call an external COM based component in order to send email (that's what you are doing if you are creating a CDO message --- anytime you have a CreateObject call in your asp code, that is COM), the asp code will appear to hang if the external component takes a long time to respond. For example, most SMTP components will synchronously try to send the message to the SMTP server blocking your asp code from executing until the email message is sent. This becomes a problem on very busy SMTP servers, as they can be very slow to respond to connection requests and to SMTP commands. Another bad situation is that many ISP's/hosts attempt to throttle the speed you can send email by purposefully making their SMTP servers respond slowly. Even worse, some hosts will go so far as to actually make subsequent connections over a set time period progressively slower. This can significantly impact your site performance since you are typically having your page code blocked during the SMTP send.
The best solution would be to use a host or SMTP server that does not enforce such restrictive measures. Barring that, there is a way to work around this by using message queuing. If you are using CDO, this means you have to configure the Microsoft SMTP Service on your IIS web server for use. This can be configured properly even if you do have other SMTP software on the IIS machine. Once the Microsoft SMTP Service is running on your IIS server, it will be able to queue email on the server and forward them to the configured SMTP server asynchronously to your application / page code. When configuring the Microsoft SMTP Service, you must define what it calls a "smart host". This is simply the SMTP server you are going to route the outbound email to for delivery on your network.
Once you have that configured, you just have to change your code that uses CDO to queue the email message instead of trying to send it. In your CDO code, you should have a line that sets CDO field values which look something like this:
objFlds.Item("http://schemas.microsoft.com/cdo/configuration/sendusing") = 2
You want to change the value for the "sendusing" field from a value of 2 to a value of 1. These are the enumerated values for the cdoSendUsingPort (2) and cdoSendUsingPickup (1) enums. Once you do this, you can also drop the "smtpserver" and "smtpserverport" fields as these are overridden by however your Microsoft SMTP Service is configured. Once you do this, your asp code will quickly generate the email message and it will be queued in the IIS server's mail pickup folder. So your application / page code will run much faster. The outgoing emails will potentially accumulate in the queue folder as the SMTP Service slowly works on delivering them in the background. It doesn't make the email get send any faster, but it does prevent your code from blocking due to a slow SMTP server.
I later found that the actual sending of the email was not causing the problem but the fact that I was generating the HTML body for the email by retrieving HTML from another ASP page (via the XML object).
I tried various things to fix the problem including switching mail components (to Jmail) and using different versions of the XML object but the problem would still occur intermittently.
In the end I changed the code to generate the HTML for the email body instead of calling another ASP page and reading it's response.
Eliminating use of the XML object seems to have resolved the problem but the cause was never found.
Related
When a unavailable url is accessed, we internally raise an exception and email to support team. We do this to identify is there is hidden error in our web application. Couple of days back, suddenly there was a huge number of access to unavailable url which added load to server and casued SMTP to queue large exception emails. This attempt has brought IIS completely down and none of the applications are accessible.
How to prevent this? Is there any other option like firewall etc to disallow continues request from same ip. I have seen this behavior in google. How can we achieve that?
I'd suggest caching already sent notifications. Before your application sends email, it can check if this error is already reported.
And you can set the cache validity to, say 1 minute, so you get maximum 1 same email/minute.
It is quite easy to implement in ASP.NET.
i have to write application for sending newsletter.
what is the best way to send newsletter thoundands of users?
My requirement is
Each mail is seprately as To :
Every mail has unique Unsubscribe link
Is is good to use SMTP mail class of .net?
I look aound may questions in so but can't decide which approcah i should go?
There are many suggestions
Multi threaded Windows service
Use Mail Server
Add thread.sleep(2000) between each send.
can anyone suggest good way to imepement this?
I would not recommend asp.net webpage to send, even if you do start it in a separate background thread. I would think you run the risk of the server recycling your process in the middle of the send, which would mess it up. You really need to write some kind of separate service or application to send your emails.
The simplest option would be to just create a quick and dirty console or windows form application.
Also logging is critical just like the other poster said. If it fails you want to know exactly what got sent out and where it stopped so that when you restart it you don't mail all the people who it did work for again. You want to be able to input the starting point for the send, so if you need to restart at number email #5000 you can.
The classes in System.Net.Mail namespace will work just fine for sending your mail.
One of the biggest problems will be finding a email host that will let you send so many emails. Most email hosts have throttling and sometime it changes depending upon server conditions so if the server is being heavily used then the email limits will be more restrictive, and you may only get to set 500 emails per hour.
We have a newsletter that goes out to around 20000 people as separate emails and we had to play around with the delay between emails until we found one that would work for our email host. We ended up with 1.2 sec between emails, so that might be a good starting point.
I think there are email hosts specialize in bulk mailings though so if you get one of those it might not be a problem.
Also if you host your own email this may not be a problem. And if you do host your own mail you will have the option of dropping the mail in the pickup directory and you could just dump it all in there as fast as you want, and let the email service pick it up at it's own pace.
EDIT: Here is the settings to add to the config file for setting the pickup directory
<system.net>
<mailSettings>
<smtp from="support#test.com" deliveryMethod="SpecifiedPickupDirectory" >
<specifiedPickupDirectory pickupDirectoryLocation="Z:\Path\To\Pickup"/>
</smtp>
</mailSettings>
</system.net>
Definitely do not do this in ASP.NET. This is one of the biggest mistakes that new web developers make.
This needs to be a windows app or service that can handle this much volume.
I've written pages that send emails, but not nearly the volume yours will. Nonetheless, I would recommend the following based on code I have implemented in the past:
Use the web application to write out the email and all the recipient addresses to database table(s).
Have a process that is outside of ASP.NET actually send the emails. This could be a vbs file that is set up as a scheduled task, or (preferably) a windows service. The process would take the text of the email, append the unsubscribe link, and once sent successfully flag the database record as sent. That way, if the send fails, it can try again later (the send process loops over all the records flagged as unsent).
If you need a log of what was sent and when, you just need to keep the sent records in the database tables. Otherwise, just delete the records once sent successfully.
IMHO sending emails within the ASP.NET worker process is a bad idea because you don't know how long it will take and if the send fails there's little opportunity to retry before the page times out.
Create a webpage to "Design" the newsletter in. When they hit Send, queue the newsletter up somewhere (database) and use another program (windows service, etc) to send the queued letter. This will be many times more effecient and potentially fault tolerant if designed properly.
I have written a Newsletter module (as part of a bigger system) in ASPNET MVC 2, Entity Framework and using the System.Net.Mail namespace. It is kicked off in view and actually just runs in a controller with a supporting method to do the send. As each email is sent I track whether there is a hard bouce (an exception is thrown) and I update that database record stating a fail with the exception, otherwise I update the record stating success. We also do personalisation so we have 'tags' that get replaced by an extra field in the database (stored as XML for flexibility). This helps handle an unsubscribe function.
My code is quite simple (please don't flame me for using exception handling as business logic ;) and it works like a charm.
This is all done on a VPS at http://maximumasp.com which also hosts 4 sites with pretty decent traffic. We use their SMTP servers. We notified them that we needed this service and have had no problems relationship-wise.
We had 2GB of RAM on the machine running Windows 2008 and it was doing 6 emails/sec. We bumped it up to 3GB as the web sites needed it and now the mailout is doing about 20emails/sec. Our mailouts range from 2,000 to 100,000 email addresses.
In short, ASP.NET can be used to handle a mailout, and if you add in some logic to handle record updating the worry of losing your way mid-send is mitigated. Yes there are probably slicker ways to do this. We are looking in to MQMS and threading, and separating that out to windows service to make it more stable and scalable as we put more clients and larger lists on, but for now it works just fine with reasonable reporting and error handling.
I am writing an application that will need to send a massive amount of emails to our students who will be selected from our database (each email will be personalized to the extent that will include their name, course of study etc...so needs to be sent one at a time).
I could do this looping over an SmtpClient, but I'm afraid that with the numbers I'm trying to send, I'll ultimately run into timeout issues or my thread being killed because of lack of machine resources.
At this point I'm just looking for suggestions of a better way to handle this, or if looping over SmtpClient is an ok solution, how I should go about handling it to prevent what I posted above.
Would a web service be a better alternative?
Please advise,
TIA
My suggestion would be to batch this out. Do not try to run ASP.NET code to create 20K emails and send them out as you are bound to runinto timeout and performance issues. Instead populate a table with recipient, subject, body and begin a batch process from a windows service. This way your code is executed in a way where lag can be managed, instead of having a web page wait for the request to return.
Ok, first - this is hardly massive, I have been handling 50.000 emails+
Let the emails be written to a FOLDER - directory. Then use the local SMTP service you can install, pointing it at the folder as pickup directory. This will at least make sure you have a decent buffer in between (i.e. you can finish the asp.net side, while the emails are not sent at that point).
What about using Database Mail tool provided by SQL Server itself. You can still use asp.net but Email will be sent by SQL Server and all you have to do call the stored procedure and leave things to SQL Server.
I wouldn't recommend batch option since there won't be any optimization or queue thing unless you have to put a lot of effort to do so.
Database Mail tool provides queue and priority options as well. If a problem occurs, the e-mail will be queued again and sent later but the other ones will be still being sent.
It is called Database Mail in SQL Server 2008 and SQL Mail in previous versions.
For more information, please check the links below :
http://blog.sqlauthority.com/2008/08/23/sql-server-2008-configure-database-mail-send-email-from-sql-database/
http://msdn.microsoft.com/en-us/library/ms175887.aspx
You could use javascript on a timer to request the script which sends mail in small chunks that wont time out. Then you'd call the script from the browser. Add a progress bar, authentication, etc.
You don't need a web service, but rather a way to batch the emails into a queue (perhaps an "Email_Queue" table in the DB). Then a Windows service running on a server could read through the queue in a first-in/first-out basis at reasonable chunks at a time being sent to the SMTPClient, removing items from the queue as they are processed. You would probably need to run some measurements to determine what the chunk size and delay would be for your mail server.
Hai Guys,
My application deals scheduled mail concept (i.e) every morning 6.00 am my users gets a remainder mail about their activities for the day... I dont know how to do this.... Many told use windows service but i will host my website on a shared server i may not get rights to do windows service... Is there any dll for sending mails at a schduled time through asp.net application ..please help me out guys......
You cant do much in a shared hosting. Try upgrading your hosting or else write a windows service, to run on your machine, which will call an asp.net which can send out emails. Of course your machine has to be switched on all the time or at least during 6:00 AM :). You will have to take proper steps to avoid unauthorized request for that aspx page.
you can check this article too: http://www.codeproject.com/KB/aspnet/ASPNETService.aspx
You can't really do this with ASP.Net. ASP.Net is for web pages - which are reactive to HTTP requests.
You need a scheduled task or a service. All a website can do is respond to requests. I guess you could program the functionality into a web page and have a remote process request the page every morning - but what happens if someone else requests the page?
You can either have a program that runs constantly and has a timer or a loop that checks the time of day and then sleeps for a really long time and when the timer goes off or it's the right time of day it sends an email, or you can launch a program as a scheduled task. The first method can also be implemented as a service if you would like. Keep in mind you dont need ASP.Net to send emails, all you need is a console application that uses System.Net.Mail. Check out the mailer sample on MSDN for a very simple idea.
One other thing you can consider: IIS has an smtp service that you can install and it uses a pickup directory to send mail. You write an email to the pickup directory as an .eml file and IIS grabs it and sends it almost immediately. If you do that, you'll still have to write the emails (System.net.Mail will write the .eml files from a MailMessage, just set SmtpClient.DeliveryMethod to SpecifiedPickupDirectory or PickupDirectoryFromIIS and call SmtpClient.Send) but it will then send them for you. You'll still need to schedule something somehow so this might not be all that more useful but I thought I'd at least let you know that it exists.
One thing to be aware of: when the IIS SMTP service reads the send envelope of the .eml file, the order of the Sender and From headers is significant; if the From header appears before the Sender header then the MAIL FROM command will use the From header, which is incorrect (and MS won't be fixing this one). This appears to be an issue ONLY with the IIS SMTP service as it hasn't been reported anywhere else that I'm aware of. Reversing the order of the headers is the work-around. By default SmtpClient always writes the From header first. I'm aware of the issue and IIS isn't fixing it but I may be able to get a fix into SmtpClient for the .NET 4.0 RC build that re-orders the headers for you but no promises.
If you happen to have it handy (and I assume you do), you can use a SQL Server Agent job to make a request to an ASP.NET page that sends the email.
Here's some example code:
http://nicholasclarke.co.uk/blog/2008/01/16/web-request-from-sql-server-via-c/
Of course, since you're using SQL Server to call CLR code anyway, you could just have that code send out the emails (via System.Net.Mail) rather than requesting a page on IIS to do so. To do this, SQL Server would need:
Access to all of the data needed to send the emails
Outbound firewall access to send an email
CLR code that encapsulates all of the logic needed to know where/what to send.
Okay this is interesting, and what I did fits silky's definite of 'cheating', but no it was pretty cool for me.
What I did was spawn a new thread from ASP.Net code (it was possible on that host), and that thread did the scheduled job.
I checked whether the thread was alive (which is pretty easy) on every visit to the website (not so reliable I know, but it worked cause that website has plenty of visitor).
If at all you do this
Treat this as a stop-gap while you arrange to get a dedicated host or VPS.
Rest assured that the hosting company will kill your thread and withdraw permissions when they discover you're doing this.
Scenario:
localhost receives the current HttpRequest with 3 hidden inputs and a posted file. I must then forward this form data to an external image host and get the response.
See the System.Net.WebClient and related classes. You can use them to create a request to the remote server and handle the response. Also get Fiddler to help you replicate what the browser sends.
I hate doing this. It wastes my server's bandwidth and ties up IIS threads as well as using my server's CPU. It sucks and it's worth avoiding at all cost. Many services like, one that comes to mind is fliqz, provide a mechanism such that the files are uploaded directly from the client to their server (bypassing yours) and then they make a request to your server passing it various info on the query string.