I am sending email from application. My problem is when your type email address means format is correct but it may be not available anywhere.so when I am trying send such email address using SMTP through application, so how to track fail-over notification if intended recipient not found.
please suggest any approach.
There is no standard way of doing this. You might be able to make it work in some cases by parsing incoming email looking for delivery failure notices but it'll be a lot of work to keep that parsing code up to date. So at best you'll only get some of the notices. If you get a notice at all. The recipient's SMTP server may not send you anything, or the notice might get lost on it's way back to you.
The only way you are reliably get this sort of information is to host the SMTP server yourself, and deliver directly to the recipients SMTP server. In that case the SMTP server knows the status of the email's delivery and could report that to your email client via some non-standard back channel.
Note: Hosting your own SMTP server is non-trivial. And you will probably need to be on a fixed IP otherwise external SMTP servers will treat your email as spam. In case you're thinking of running one over a home connection or something.
I'm usign amazon cloud services to host my webpage. Our web site, actually sends a lot of emails per hour. In one instant our server could be asked to send 30 mails or more.
Sometimes our clients complaint about not getting emails from the web, which is connected to our mail server to send emails. This doesn't happen if we send the email directly from our addresses to theirs, so I'm pretty much know is the web page who's causing the problem.
The thing is I don't know what is happening and neither know what to look for. I've checked memory and cpu of that server and everything seems to work fine
make sure your website sends the messages with a correct bounce address (aka envelope sender address). this does not have to be the same thing as the address in the From: header. by default, this is often something like "apache#www.example.com" - I don't know about amazon). these types of bounce addresses are bad because usually you don't receive the error message if something goes wrong. use a real email account. To check what bounce address you currently use, look at the message source of a received mail and see the Return-Path header.
check the logs of your mailserver for those missing messages. either it reports an error (in which case you should get the error to your bounce address) or it reports the message as sent to the target server (in which case you tell your clients to check THEIR maillogs since you can prove you have sent the message)
I have an e-mail account with hostgator. I would like to build a console application (later a service application) that will check a mysql database for e-mails that need to be sent out and will process them by sending a certain number of e-mail every so many seconds. These e-mails will each have a 2-3mb pdf price sheet attached to be sent to our regular customer base. About 500 are set up to receive e-mails.
My question is: Should I connect to hostgator directly and send the
e-mails or should I use the IIS Virtual Server Relay and have it
connect to hostgator?
The only thing I can think of is if Hostgator were down the virtual relay might be a good option since it has retries. There again, I guess I could put some try/catch in the code where if it doesn't connect to hostgator or if their is a problem it will go to the timer and wait x minutes before retrying to process e-mails.
We have found that the easiest approach is to generate the outgoing emails and drop them in the inetpub\mailroot\pickup folder and let the SMTP service handle them (you can set it up to forward the emails to the appropriate host).
This falls firmly under the category of not re-inventing the wheel: the SMTP service easily handles the situation when the connection to the mail server is down, retries, and all of the other "fun" stuff that you would otherwise have to implement in your code if you handle the SMTP sends directly.
We have set up a system where notifications get sent to a user with the following From address format: user-{0}#aol.com (replace {0} with an ID)
This way we can track what user we sent the message to originally. This format is not likely to change for various reasons. The issue we are running into is this: every email we send out with a dynamic address is creating a new SMTP relay.
My knowledge of relays is very limited. Our host (GoDaddy) limits SMTP relays to 250 per day. This is an application that potentially will be sending out thousands of emails per day.
Is my assumption that every 'unregistered' email address we use opens a new relay, correct? If so, are there any services or hosts that provide unlimited relays for a reasonable price?
Thanks.
so my assumption that every 'unregistered' email address we use opens a new relay, correct?
Relay is basically a classification. every email sent via relay opens an SMTP connection on the mail server and not "a new relay"...that said, It might be cheaper, if you can, to set up your own sending SMPT server. It comes as a component of IIS. If you need any additional information on setting this up, let me know.
Godaddy, yes, due to the different plans. You can try any other email providers like google and yahoo as well. Just make sure to setup a "catch" all mailbox for undelivered mails and any responses.
For the past few weeks, I've been trying to learn about just how email works. I understand the process of a client receiving mail from a server using POP pretty well. I also understand how a client computer can use SMTP to ask an SMTP server to send a message. However, I'm still missing something...
The way I understand it, outgoing mail has to make three trips:
Client (gmail user using Thunderbird) to a server (Gmail)
First server (Gmail) to second server (Hotmail)
Second server (Hotmail) to second client (hotmail user using OS X Mail)
As I understand it, step one uses SMTP for the client to communicate. The client authenticates itself somehow (say, with USER and PASS), and then sends a message to the gmail server.
However, I don't understand how gmail server transfers the message to the hotmail server.
For step three, I'm pretty sure, the hotmail server uses POP to send the message to the hotmail client (using authentication, again).
So, the big question is: when I click send Mail sends my message to my gmail server, how does my gmail server forward the message to, say, a hotmail server so my friend can recieve it?
Thank you so much!
~Jason
Thanks, that's been helpful so far.
As I understand it, the first client sends the message to the first server using SMTP, often to an address such as smtp.mail.SOMESERVER.com on port 25 (usually).
Then, SOMESERVER uses SMTP again to send the message to RECEIVESERVER.com on port 25 (not smtp.mail.RECEIVESERVER.com or anything fancy).
Then, when the recipient asks RECEIVESERVER for its mail, using POP, s/he recieves the message... right?
Thanks again (especially to dr-jan),
Jason
The SMTP server at Gmail (which accepted the message from Thunderbird) will route the message to the final recipient.
It does this by using DNS to find the MX (mail exchanger) record for the domain name part of the destination email address (hotmail.com in this example). The DNS server will return an IP address which the message should be sent to. The server at the destination IP address will hopefully be running SMTP (on the standard port 25) so it can receive the incoming messages.
Once the message has been received by the hotmail server, it is stored until the appropriate user logs in and retrieves their messages using POP (or IMAP).
Jason - to answer your follow up...
Then, SOMESERVER uses SMTP again to send the message to RECEIVESERVER.com on port 25 (not smtp.mail.RECEIVESERVER.com or anything fancy).
That's correct - the domain name to send to is taken as everything after the '#' in the email address of the recipient. Often, RECEIVESERVER.com is an alias for something more specific, say something like incoming.RECEIVESERVER.com, (or, indeed, smtp.mail.RECEIVESERVER.com).
You can use nslookup to query your local DNS servers (this works in Linux and in a Windows cmd window):
nslookup
> set type=mx
> stackoverflow.com
Server: 158.155.25.16
Address: 158.155.25.16#53
Non-authoritative answer:
stackoverflow.com mail exchanger = 10 aspmx.l.google.com.
stackoverflow.com mail exchanger = 20 alt1.aspmx.l.google.com.
stackoverflow.com mail exchanger = 30 alt2.aspmx.l.google.com.
stackoverflow.com mail exchanger = 40 aspmx2.googlemail.com.
stackoverflow.com mail exchanger = 50 aspmx3.googlemail.com.
Authoritative answers can be found from:
aspmx.l.google.com internet address = 64.233.183.114
aspmx.l.google.com internet address = 64.233.183.27
>
This shows us that email to anyone at stackoverflow.com should be sent to one of the gmail servers shown above.
The Wikipedia article mentioned (http://en.wikipedia.org/wiki/Mx_record) discusses the priority numbers shown above (10, 20, ..., 50).
You're looking for the Mail Transfer Agent, Wikipedia has a nice article on the topic.
Within Internet message handling services (MHS), a message transfer agent or mail transfer agent (MTA) or mail relay is software that transfers electronic mail messages from one computer to another using a client–server application architecture. An MTA implements both the client (sending) and server (receiving) portions of the Simple Mail Transfer Protocol.
The terms mail server, mail exchanger, and MX host may also refer to a computer performing the MTA function. The Domain Name System (DNS) associates a mail server to a domain with mail exchanger (MX) resource records containing the domain name of a host providing MTA services.
You might also be interested to know why the GMail to HotMail link uses SMTP, just like your Thunderbird client. In other words, since your client can send email via SMTP, and it can use DNS to get the MX record for hotmail.com, why doesn't it just send it there directly, skipping gmail.com altogether?
There are a couple of reasons, some historical and some for security. In the original question, it was assumed that your Thunderbird client logs in with a user name and password. This is often not the case. SMTP doesn't actually require a login to send a mail. And SMTP has no way to tell who's really sending the mail. Thus, spam was born!
There are, unfortunately, still many SMTP servers out there that allow anyone and everyone to connect and send mail, trusting blindly that the sender is who they claim to be. These servers are called "open relays" and are routinely black-listed by smarter administrators of other mail servers, because of the spam they churn out.
Responsible SMTP server admins set up their server to accept mail for delivery only in special cases 1) the mail is coming from "its own" network, or 2) the mail is being sent to "its own" network, or 3) the user presents credentials that identifies him as a trusted sender. Case #1 is probably what happens when you send mail from work; your machine is on the trusted network, so you can send mail to anyone. A lot of corporate mail servers still don't require authentication, so you can impersonate anyone in your office. Fun! Case #2 is when someone sends you mail. And case #3 is probably what happens with your GMail example. You're not coming from a trusted network, you’re just out on the Internet with the spammers. But by using a password, you can prove to GMail that you are who you say you are.
The historical aspect is that in the old days, the link between gmail and hotmail was likely to be intermittent. By queuing your mail up at a local server, you could wash your hands of it, knowing that when a link was established, the local server could transfer your messages to the remote server, which would hold the message until the recipient's agent picked it up.
The first server will look at DNS for a MX record of Hotmail server. MX is a special record that defines a mail server for a certain domain. Knowing IP address of Hotmail server, GMail server will sent the message using SMTP protocol and will wait for an answer. If Hotmail server goes down, GMail server wiil try to resend the message (it will depend on server software configuration). If the process terminates ok, then ok, if not, GMail server will notify you that he wasn´t able to deliver the message.
If you really want to know how email works you could read the SMTP RFC or the POP3 RFC.
All emails are transferred using SMTP (or ESMTP).
The important thing to understand is that the when you send message to someguy#hotmail.com this message's destination is not his PC. The destination is someguy's inbox folder at hotmail.com server.
After the message arrives at it's destination. The user can check if he has any new messages on his account at hotmail server and retrieve them using POP3
Also it would be possible to send the message without using gmail server, by sending it directly from your PC to hotmail using SMTP.
Step 2 to 3 (i.e. Gmail to Hotmail) would normally happen through SMTP (or ESMTP - extended SMTP).
Hotmail doesn't send anything to a client via POP3. It's important to understand some of the nuances here. The client contacts Hotmail via POP3 and requests its mail. (i.e. the client initiates the discussion).