This is a discussion on Send a mail without going to spam within the PHP Language forums, part of the PHP Programming Forums category; Gordon Burditt wrote: >>>> I like the way you wobble back and forth on that. >>&...
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Gordon Burditt wrote:
>>>> I like the way you wobble back and forth on that. >>>> It's not a realy - except when it is. >>> Nope, I stand that most public MTA's are not relays. >> OK, Jerry - but that requires a very wrong interpretation of the word >> "Transfer". > > A typical public MTA that is NOT considered an open relay will > permit mail traffic that is: > > (a) destined for mailboxes that it handles (incoming mail from > anywhere is allowed, subject to SPAM filtering). Note that > the mailboxes are NOT necessarily on the same machine. In > large setups the public MTA may be a border MX machine with > few (e.g. "root" only) or no mailboxes and they pass the mail > to the servers with the mailboxes. This is not a relay. > or (b) sent in by trusted customers or from trusted locations to the > world (outgoing mail from my customers is allowed). This may > be checked by a number of methods: > (1) Authenticated SMTP, with or without SSL > (2) POP-before-send: you must check your mailbox from the > IP address you are using within X minutes before sending > mail out. > (3) SSL with user certificates > (4) Using extensions to POP3 or IMAP to send mail during > a mail-fetching session. > (5) Allowing any mail from IP blocks owned by the ISP > (6) Combinations of these, such as (5) from DSL or dialup > lines and (1) or (2) from "roaming" customers > (7) There's all sorts of other methods also. > True, but the majority of the MTA's on the internet are not configured these ways. Those that are are generally ISP's or shared hosting companies. And a few are owned by spam filtering companies. There are many more MTA's out there owned by individuals, companies, etc. which only match (a). > This does not address the subject of SPAM filtering or virus scanning. > > Incidentally, there's a subtle difference between "relay" and > "forward". This terminology might not be universal but its in > use at some ISP abuse departments. > > Let's suppose that there is a mail service that will accept mail > to me at me@service.com and forward it to any mailbox I designate. > I designate my mailbox at my local ISP, me@isp.com . When someone > does a spam run against the @service.com addresses, service.com may > get accused of being an open relay when it doesn't really deserve > it. > > A spammer connects to the service.com mail server and drops off a > penis enlargement ad for me@service.com. Their server transfers it > to the mail server at isp.com, which delivers into the me@isp.com > mailbox. This is a *forward*. The *customer* requested the routing > from service.com to isp.com. > > A spammer connects to the service.com mail server and drops off a > penis enlargement ad for you@aol.com. Their server transfers it to > the mail server at aol.com. Unless the spammer had authentication > or permission to use the service.com mail server, this makes it an > open relay. The *spammer*, not the AOL customer, requested the > routing from service.com to aol.com. > Yes, I am quite aware of the difference between relaying and forwarding. > >> Seriously - on this I consider myself an honest expert. Back in 95, I >> built the first Fax-Over-IP protocol, as you've heard me say once or >> twice before. >> >> In that effort, I spent a year *constantly* consulting with Marshall >> Rose and he gave me an excellent education on this. If you don't know >> who he is, check the SMTP specification; his name is on it. >> >> I can't claim his expertise as my own - but when you consider that MTA >> stands for Message Transfer Agent, the truth that it is a relay becomes >> quite self-evident. >> >> >>>> That last, of course, is why I suggested that the OP use an SSL >>>> secured mail relay. >>> Which has absolutely no effect on whether the relay is secure or not. >>> All SSL does is encrypt the data. >> Wow - could you BE more self-contradictory? > > SSL encrypts the data so the thief of a customer (using a phony > credit card number) can rip off the thief running the web site > before any other thief (such as the FBI or dishonest ISP employee) > can get to the card number. SSL does not identify the customer to > the web site, unless it insists on user certificates. > > It works the same way with email. A spammer can securely shower > the whole internet with penis enlargement ads while making it > difficult for someone tapping the net to see what's in the email > until their copy lands in their mailbox. > I never claimed otherwise. All I said was that SSL encrypts the data while it was being sent. It can be found in decrypted form on both ends of the link. > >>> When an MTA receives a message and places it in a POP (or IMAP) mailbox, >>> it is called "Delivery", not relay. Relay is used to indicate passing >>> on to another MTA. > > Many corporate and ISP setups have "border MX machines" running a > MTA which receives the email and passes it on to one of a bunch of > another machines which actually hold the mailboxes. The "border > MX machines" have few or no mailboxes themselves. > True, but this is going to an intranet, as I mentioned earlier. I'm talking about internet relays. >> And how does it get from the outgoing MTA, to the incoming MTA? Relay. >> Thus - an MTA that does not relay, is merely a POP. > > I suggest not using the abbreviation "POP" to refer to "Point of > Presence" when discussing mail protocols. There's another meaning > for that TLA (And I don't mean Tokyo Law Association). Similarly, > don't use "IP" to mean "Intellectual Property" when discussing TCP > port numbers. > >> btw - it would be more accurate for you to say POP3 Server, because POP >> has a very specific tele-communications networking meaning beyond >> internet email. > > I never referred to POP meaning "Point of Presence". Every time I used it was 'Post Office Protocol". And when I referred to IP, I was talking about Internet Protocol. Nothing different. -- ================== Remove the "x" from my email address Jerry Stuckle JDS Computer Training Corp. jstucklex@attglobal.net ================== |