   smtp
  S: 220 smtp.example.com ESMTP PostfixC: HELO relay.example.orgS: 250 Hello relay.example.org, I am glad to meet youC: MAIL FROM:<bob@example.org>S: 250 OkC: RCPT TO:<alice@example.com>S: 250 OkC: RCPT TO:<theboss@example.com>S: 250 OkC: DATAS: 354 End data with <CR><LF>.<CR><LF>C: From: "Bob Example" <bob@example.org>C: To: Alice Example <alice@example.com>C: Cc: theboss@example.comC: Date: Tue, 15 Jan 2008 16:02:43 -0500C: Subject: Test messageC:C: Hello Alice.C: This is a test message with 5 headers and 4 lines in the body.C: Your friend,C: BobC: .S: 250 Ok: queued as 12345C: QUITS: 221 Bye{The server closes the connection}this is a conversation between server avd clinet communication by smtp i wanna know what is the significance of the string written after HELOthat is what does relay.example.org representsif i from my home wants to use smtp , what iam supposed to write in place of relay.example.org  ?thanks in advance   
Quote:Original post by iamspecialthis is a conversation between server avd clinet communication by smtp i wanna know what is the significance of the string written after HELOthat is what does relay.example.org representsif i from my home wants to use smtp , what iam supposed to write in place of relay.example.org  ?thanks in advanceIt doesn't mean anything really, the only thing I've seen it used for is logging purposes. RFC 821 says:Quote:HELLO (HELO)This command is used to identify the sender-SMTP to thereceiver-SMTP.  The argument field contains the host name ofthe sender-SMTP.The receiver-SMTP identifies itself to the sender-SMTP inthe connection greeting reply, and in the response to thiscommand.This command and an OK reply to it confirm that both thesender-SMTP and the receiver-SMTP are in the initial state,that is, there is no transaction in progress and all statetables and buffers are cleared.Also, if you're sending mail from your own machine, you should be relaying it to your ISP, a lot of mail servers won't accept mail from just anyone.   ;Quote:Original post by Evil SteveAlso, if you're sending mail from your own machine, you should be relaying it to your ISP, a lot of mail servers won't accept mail from just anyone.does that mean that i have to use thishelo (my isp server name )and then it will be ok ;Quote:Original post by iamspecialQuote:Original post by Evil SteveAlso, if you're sending mail from your own machine, you should be relaying it to your ISP, a lot of mail servers won't accept mail from just anyone.does that mean that i have to use thishelo (my isp server name )and then it will be okNo, you need to connect to your ISPs mail server rather than directly to, say mail.google.com or whatever. Your ISP will then relay the mail to the target server for you. You might be doing this already of course. When you're connected to your ISPs mail server, it won't really matter what you put after "HELO".   ;  The string after the HELO (or EHLO) is the name that the connecting server (i e, you) think you have.The relaying rules are typically something like:1) Is the user authenticated as one of my trusted users?  -> allow relay2) Is the incoming mail address destined for one of my users?  -> allow receipt3) Else give up and disallow relayMany servers add additional tests, such as "is the sender IP on a list of known spammers" or "does there exist a proper reverse DNS for the sender IP." There's also the SPF (sender policy framework) record.Note that many mail servers have the entire Comcast client network marked as "known spammers," so don't try running a mail server on a cable modem. I have, however, run a mail serer over proper DSL (with proper reverse DNS) for a long time, and it's worked fine.Except the spam traffic started becoming so heavy that my dual-core Core 2 6550 with 4 GB of RAM couldn't keep up, and it was saturating my downlink constantly with just spam, even when checking reverse DNS, RBL and SPF records. At that point, I decided to give up and moved my mail hosting to google apps :-/It was fun while it lasted, though (like, for the last 10 years!)