Re: [exim/fetchmail] A day in the life of an email
Hello, Just one minor comment, since others seem to be handling the query... Mark Phillips wrote: ... 3. Fetchmail feeds this email into some black box (I don't understand this bit - is it a file or is it a program that is sitting around waiting for such events???). ... There is no black box. Fetchmail communicates directly with exim thru port 25 using the SMTP protocol. Actually, there's another way you can hand a message to exim, and that is by invoking it directly, as /usr/sbin/exim (or /usr/sbin/sendmail). You can configure fetchmail to use either method. BTW, you might need to configure exim to accept invalid sender addresses from fetchmail, but I've forgotten how I did that. 5. I then decide to send a message to [EMAIL PROTECTED] I compose an email in pine which puts the message in the black box talked about above. ... As above, pine will communicate directly with port 25 or your local machine and talk to exim. I would suspect that most programs would call /usr/sbin/sendmail, because that's a lot easier to do. Certainly elm has that filename hard-coded into it, and so does mutt. /usr/sbin/sendmail is another name for exim, which then does whatever it's supposed to with the message - typically, it'll either write it to someone's mailbox, telnet 25 to another host, or write it into its private area to deal with it later. HTH Jiri [EMAIL PROTECTED]
Re: [exim/fetchmail] A day in the life of an email
On Tue, 8 Dec 1998, Mike Touloumtzis wrote: 3) Set qualify_domain = ist.flinders.edu.au to make your locally generated mail appear to originate from that machine. This is potentially not necessary if ist.flinders.edu.au accepts mail for *.flinders.edu.au and the MX records are set up correctly in the DNS, but I don't think it can hurt. Thanks for your help. Things are almost working. Only one problem at the moment. Setting the qualify_domain to ist.flinders.edu.au works well at making my email appear to originate from uni. The only problem is when at home I email to mark, the email ends up at my account at uni. This is not the desired behaviour. mark is my local username and the email should have been sent locally. For some reason it is not. I presume that because I addressed the email to mark not to [EMAIL PROTECTED], it decided to qualify it for me to [EMAIL PROTECTED]. Is there any way of getting it to make the from address appear to be [EMAIL PROTECTED] while at the same time, allowing mark to be completed as [EMAIL PROTECTED]? Cheers, Mark. _/\___/~~\ /~~\_/~~\__/~~\__Mark_Phillips /~~\_/[EMAIL PROTECTED] /~~\HE___/~~\__/~~\APTAIN_ /~~\__/~~\ __ They told me I was gullible ... and I believed them!
Re: [exim/fetchmail] A day in the life of an email
On Thu, Dec 10, 1998 at 06:17:20PM +1030, Mark Phillips wrote: On Tue, 8 Dec 1998, Mike Touloumtzis wrote: 3) Set qualify_domain = ist.flinders.edu.au to make your locally generated mail appear to originate from that machine. This is potentially not necessary if ist.flinders.edu.au accepts mail for *.flinders.edu.au and the MX records are set up correctly in the DNS, but I don't think it can hurt. Thanks for your help. Things are almost working. Only one problem at the moment. Setting the qualify_domain to ist.flinders.edu.au works well at making my email appear to originate from uni. The only problem is when at home I email to mark, the email ends up at my account at uni. This is not the desired behaviour. mark is my local username and the email should have been sent locally. For some reason it is not. I presume that because I addressed the email to mark not to [EMAIL PROTECTED], it decided to qualify it for me to [EMAIL PROTECTED]. Is there any way of getting it to make the from address appear to be [EMAIL PROTECTED] while at the same time, allowing mark to be completed as [EMAIL PROTECTED]? Hmmm... the first thing to do is to check to see if mail for yourhostname.flinders.edu.au ends up at ist.flinders.edu.au when sent from the outside world. If this is the case, then you can just use your hostname+domain for qualify_domain and replies should work OK (this is the way my company's setup works; mail to [EMAIL PROTECTED] will get to me). Try hostname.ist.flinders.edu.au as your local host/domain + qualify_domain too, as 'ist' is not the real hostname of your smarthost--see below). I played around with 'dig' for a sec, and it looks this depends on frodo.cc.flinders.edu.au (AKA flinders.edu.au, and the catchall mail destination for your university according to the MX records) if your machine is hostname.flinders.edu. If your machine is hostname.ist.flinders.edu, it depends on ist.flinders.edu.au, AKA adam.ist.flinders.edu.au. Frodo resolves to a different IP than adam, so these are probably distinct machines. One or both of these machines might know enough about you to get mail to your spool just based on your username. 'ist' sounds like a better bet, as it's more specific to you. frodo.cc.flinders.edu.au's SMTP server accepts mail for [EMAIL PROTECTED], but that doesn't mean anything nowadays; many servers delay bounces to make it harder for spammers to verify addresses. The only way to find out for sure is to try it. Note that the success of this may also depend on whether or not your smarthost will rewrite your email address. Sendmail has some advanced anti-spam features to verify senders, and a bogus hostname might throw it. Again, the only way to find out is to try. Barring this, your best option is probably to use the address rewriting features of exim (set your real hostname+domain as the qualify_domain, but rewrite them to the smarthost for mail that leaves the machine). This is something I have never used myself, but I took a quick look at spec.txt in the exim docs, and it appears that you can turn rewriting on and off for each director rule, and specify rewriting options for both envelope and headers. There's also the command line 'exim -brw [EMAIL PROTECTED]' that will spit out the rewritten versions for testing purposes. miket
Re: [exim/fetchmail] A day in the life of an email
Mark Phillips wrote: I am looking at setting up mail properly on my machine. I have an email account at university and use ppp to gain dial-up access to uni. I wish to set things up so that I can receive and send email from my local machine (rather than rlogin to a uni machine to read email as I do at the moment.) It is nice to have both these options available to you. Please excuse my ignorance, but I am a bit unsure about what I must do and about exactly what happens with email. Here is my current understanding of what the story is: 1. Email arrives at the mail server at uni with the address [EMAIL PROTECTED] and is stored in a spool directory there. True. 2. I contact the mail server using fetchmail, asking it very nicely to remove the email from my spool directory there, and send it to my machine at home. Fetchmail does this with the POP protocol. You have to configure the politeness level in .fetchmailrc ;) 3. Fetchmail feeds this email into some black box (I don't understand this bit - is it a file or is it a program that is sitting around waiting for such events???). Exim somehow notices that there is email coming into this black box and stores this in /var/spool/exim/input. Exim then looks and sees that the domain of the message is ist.flinders.edu.au. Fortunately this domain has been configured as the local domain in exim.conf so exim knows to distribute these messages to local users. It then sees the user is mark and so knows to distribute this to mark on the local machine. It moves the email from /var/spool/exim/input to /var/spool/mail/mark. This is not my understanding. Fetchmail is the program that translates between your university address and your local address. You configure this in your .fetchmailrc. There is no black box. Fetchmail communicates directly with exim thru port 25 using the SMTP protocol. Exim sees the mail as coming to your local machine address/username. Exim will periodically (or immediately, if configured so) move your mail from the input spool to your /var/spool/mail/mark directory. 4. I then run a program such as pine which sees there is email in /var/spool/mail/mark and enables me to read it. I have received my email. True. Although exim can be configured to further process the email and sort it into mailboxes based on criteria you give, rather than just dumping it into /var/spool/mail/mark. 5. I then decide to send a message to [EMAIL PROTECTED] I compose an email in pine which puts the message in the black box talked about above. Exim again somehow notices it and stores it in /var/spool/exim/input. It sees that banana.com is not a local domain. It decides to forward the email to some smarthost configured in exim.conf. What mechanism/protocol does it use to do this? What should the smarthost be? Should it be my home machine (I think not??). Should it be the mail server at uni? Anyway, somehow it passes the email on to some machine that somehow knows what it is doing and delivers the email. As above, pine will communicate directly with port 25 or your local machine and talk to exim. Exim sees that the mail is not from the local network, so it forwards it to the smarthost, which is your uni server. Exim talks to the uni server thru the same SMTP port 25. 6. I then send an email to [EMAIL PROTECTED] who might be a friend at uni. Again exim gets this email, but sees that the domain is ist.flinders.edu.au. I have configured this as a local domain so exim trys to deliver this to a local user. But fred is not a local user on my home machine. He is a user at uni. I want this email forwarded on to the machine at uni. How is this done? Exim knows that ist.flinders.edu.au is not local, so it sends it to the smarthost, which is the uni server. The uni server knows to give it to fred at that domain. What you may be configuring exim to do is to pretend to be a member of ist.flinders.edu.au in the headers of the email to prevent other servers from rejecting your email for lack of a proper domain. This will not confuse the uni server (at the same domain) becuase it _should_ be configured to accept mail from it's own domain. Well, I think this sums up the state of my knowledge or lack of knowledge. I would appreciate any clarifying comments/explanations/hints etc. I would appreciate any clarifications of my understanding of it also. -Mitch
Re: [exim/fetchmail] A day in the life of an email
Hi Mark, Some answers are given below. I hope they're correct; they're based on my experience in a similar situation (although my machine is behind a firewall). miket On Wed, Dec 09, 1998 at 11:00:45AM +1030, Mark Phillips wrote: I am looking at setting up mail properly on my machine. I have an email account at university and use ppp to gain dial-up access to uni. I wish to set things up so that I can receive and send email from my local machine (rather than rlogin to a uni machine to read email as I do at the moment.) Please excuse my ignorance, but I am a bit unsure about what I must do and about exactly what happens with email. Here is my current understanding of what the story is: 1. Email arrives at the mail server at uni with the address [EMAIL PROTECTED] and is stored in a spool directory there. 2. I contact the mail server using fetchmail, asking it very nicely to remove the email from my spool directory there, and send it to my machine at home. Fetchmail does this with the POP protocol. 3. Fetchmail feeds this email into some black box (I don't understand this bit - is it a file or is it a program that is sitting around waiting for such events???). Exim somehow notices that there is email coming into this black box and stores this in /var/spool/exim/input. Exim then looks and sees that the domain of the message is ist.flinders.edu.au. Fortunately this domain has been configured as the local domain in exim.conf so exim knows to distribute these messages to local users. It then sees the user is mark and so knows to distribute this to mark on the local machine. It moves the email from /var/spool/exim/input to /var/spool/mail/mark. Fetchmail connects to port 25 on your local machine. Depending on your machine's configuration, either exim is started by inetd in response to this, or exim is running as a daemon and was already listening on that port. 4. I then run a program such as pine which sees there is email in /var/spool/mail/mark and enables me to read it. I have received my email. 5. I then decide to send a message to [EMAIL PROTECTED] I compose an email in pine which puts the message in the black box talked about above. Exim again somehow notices it and stores it in /var/spool/exim/input. It sees that banana.com is not a local domain. It decides to forward the email to some smarthost configured in exim.conf. What mechanism/protocol does it use to do this? What should the smarthost be? Should it be my home machine (I think not??). Should it be the mail server at uni? Anyway, somehow it passes the email on to some machine that somehow knows what it is doing and delivers the email. Exim uses SMTP to connect to the smarthost. For the smarthost, you want a machine with certain characteristics (see below). 6. I then send an email to [EMAIL PROTECTED] who might be a friend at uni. Again exim gets this email, but sees that the domain is ist.flinders.edu.au. I have configured this as a local domain so exim trys to deliver this to a local user. But fred is not a local user on my home machine. He is a user at uni. I want this email forwarded on to the machine at uni. How is this done? You probably don't want to your machine to have the same hostname as your university smarthost. Mail sent via SMTP is sent using an envelope, a list of addresses that is not contained within the message itself (this is what allows Bcc to work). So even though the mail that fetchmail fetches is addressed to [EMAIL PROTECTED] within the message, fetchmail uses something like mark or [EMAIL PROTECTED] as the envelope recipient when it talks to your SMTP server via TCP port 25. You don't really want fetchmail getting too smart about parsing recipients from your message, or you might end up looping the message back to all of its original recipients. Here's the way you probably want your mail to work: 1) Configure exim to treat yourhostname.flinders.edu.au as a local domain. Add whatever other local domains are needed to get fetchmail to work; this may just involve setting local_domains_include_host = true or I believe it will work to set sender_unqualified_hosts = yourhostname.flinders.edu.au 2) Remove ist.flinders.edu.au from the local_domains. This is a distinct host from yours; having your machine accept mail for it complicates the situation and shouldn't be necessary. Presumably the only thing that will ever cause mail to be routed to your machine from the outside world is fetchmail anyway. 3) Set qualify_domain = ist.flinders.edu.au to make your locally generated mail appear to originate from that machine. This is potentially not necessary if ist.flinders.edu.au accepts mail for *.flinders.edu.au and the MX records are set up correctly in the DNS, but I don't think it can hurt. 4) Set ist.flinders.edu.au as your smarthost. Smarthosts should be able to directly
