smtp - Understanding MX records with C# -


i missing piece of understanding how mail transfer works in order implement it.

i want implement smtp server, receives email message client, looks recipient mx record of domain in order deliver there.

what don't understand happens next, connect domain ip? port?

the example looking @ gmail, mx server gmail-smtp-in.l.google.com, program need connect domain on port?

thank you

read: http://www.ietf.org/rfc/rfc5321.txt

short answer:

when delivering email. mx records of domain name in question.

if mxs exist for domain attempt connect them via port 25 , deliver mail per rfc above. connect them in order of preference listed. lower numbers have higher preference. if equi-cost mx's present, free pick 1 @ random. if 1 doesn't answer try same weight mx before going higher in chain. if no mxs answer queue mail , try again..

if no mxs exist try deliver 'a' record on know port of 25 (smtp).

but really, read rfcs , become familiar them, out lot..

and related. if implementing smtp server use on internet, make sure have ability accept smtp authenticated email on submission port (587) standard port of 25. lots of networks have outbound blocks on port 25 spam abatement purposes..


Comments

Post a Comment

Popular posts from this blog

asp.net - repeatedly call AddImageUrl(url) to assemble pdf document -

i'm using abcpdf , i'm curious if can recursively call addimageurl() function assemble pdf document compile multiple urls? something like: int pagecount = 0; int theid = thedoc.addimageurl("http://stackoverflow.com/search?q=abcpdf+footer+page+x+out+of+", true, 0, true); //assemble document while (thedoc.chainable(theid)) { thedoc.page = thedoc.addpage(); theid = thedoc.addimagetochain(theid); } pagecount = thedoc.pagecount; console.writeline("1 document page count:" + pagecount); //flatten document (int = 1; <= pagecount; i++) { thedoc.pagenumber = i; thedoc.flatten(); } //now try again theid = thedoc.addimageurl("http://stackoverflow.com/questions/1980890/pdf-report-generation", true, 0, true); //assemble document while (thedoc.chainable(theid)) { thedoc.page = thedoc.addpage(); theid = thedoc.addimagetoc
Read more

java - Android recognize cell phone with keyboard or not? -

in android app, want detect user's device if device has keyboard(like motorola milestone) , show corresponding user interface. guys know how that? ! regards justicepenny http://developer.android.com/reference/android/content/res/configuration.html public int keyboard the kind of keyboard attached device. 1 of: keyboard_nokeys, keyboard_qwerty, keyboard_12key. that's it!
Read more

iphone - How would you achieve a LED Scrolling effect? -

how achieve led scrolling effect example below? led sign - led ticker emulator iphone , ipad http://img.skitch.com/20101201-rsfh4p1bajb1wp94k466pdpiuj.preview.jpg sometimes remunerates comment in other posts :) have put code you, should implement font '8pin matrix' realistic feeling. uilabel *label; - (void)viewdidload { [super viewdidload]; label = [[uilabel alloc]initwithframe:cgrectmake(10, 50, 300, 20)]; label.font = [uifont fontwithname:@"courier-bold" size:16.0]; label.backgroundcolor = [uicolor blackcolor]; label.textcolor = [uicolor greencolor]; label.linebreakmode = uilinebreakmodecharacterwrap; // otherwise "…" label.text = @"this led text scrolled "; // blanks space between [self.view addsubview:label]; [nstimer scheduledtimerwithtimeinterval:0.12f target:self selector:@selector(scrolllabel) use
Read more