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Lifecycle of an Email

Lifecycle of an Email. The care and feeding of electronic communications in their natural habitat. Lifecycle of an Email. The cast of characters Finding the trail Red herrings . The Cast of Characters. Sending mail client SMTP Server MX Server POP3 / IMAP Server Receiving mail client.

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Lifecycle of an Email

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  1. Lifecycle of an Email The care and feeding of electronic communications in their natural habitat

  2. Lifecycle of an Email • The cast of characters • Finding the trail • Red herrings

  3. The Cast of Characters • Sending mail client • SMTP Server • MX Server • POP3 / IMAP Server • Receiving mail client

  4. Supporting Cast • DNS sanity-checking • MTA-level blocklists • DCC • ClamAV • LDS • SpamAssassin • Graymail

  5. The General Case

  6. Sonic.net to Sonic.net

  7. mail.sonic.net • Ports 25, 465, and 587 • SMTP Authentication • Secure Password Authentication • STARTTLS • SSMTP

  8. mail.sonic.net • Possible causes for rejection • Unauthenticated relay • Known-bad sender address • Known-bad recipient domain • DCC Match • Very poor SMTP behavior

  9. mail.sonic.net • Logs: /sonic-logs/mail/maillog.mail Jun 18 08:00:37 b.mail.sonic.net sm-mta[8695]: l5IF0b2n008695: from=<kavan@corp.sonic.net>, size=2565, class=0, nrcpts=1, msgid=<2D1928FE480B98499E46AE0929056FA4C7851D@stingray.office.sonic.net>, proto=ESMTP, daemon=MTA, relay=fw.office.sonic.net [209.204.177.119] Jun 18 08:00:38 b.mail.sonic.net sm-mta[8702]: l5IF0b2n008695: to=<cust_svc@sonic.net>, delay=00:00:00, xdelay=00:00:00, mailer=esmtp, pri=122565, relay=mailin-01.mx.sonic.net. [208.201.249.228], dsn=2.0.0, stat=Sent (l5IF0cgx029469 Message accepted for delivery)

  10. mx.sonic.net • Port 25 • Over 2000 messages / minute average • Domain aliases handled here

  11. mx.sonic.net • Possible causes for rejection • Known-bad recipient • Off-site relay • MTA-level blocklist • ClamAV • DCC • DNS scrutiny • Very poor SMTP behavior

  12. mx.sonic.net • Logs: /sonic-logs/mail/maillog.mx Jun 18 08:00:38 e.mx.sonic.net sm-mta[29469]: l5IF0cgx029469: from=<kavan@corp.sonic.net>, size=2783, class=0, nrcpts=1, msgid=<2D1928FE480B98499E46AE0929056FA4C7851D@stingray.office.sonic.net>, proto=ESMTP, daemon=MTA, relay=b.mail.sonic.net [64.142.19.5] Jun 18 08:00:38 e.mx.sonic.net sm-mta[29469]: l5IF0cgx029469: Milter add: header: X-Sonic-SB-IP-RBLs: IP RBLs . Jun 18 08:00:38 e.mx.sonic.net sm-mta[29474]: l5IF0cgx029469: to=<cust_svc@sonic.net>, delay=00:00:00, xdelay=00:00:00, mailer=esmtp, pri=122783, relay=lds.sonic.net. [208.201.249.231], dsn=2.0.0, stat=Sent (l5IF0c9N010294 Message accepted for delivery)

  13. lds.sonic.net • Local Delivery System • .forward happens here • SpamAssassin happens here • Procmail happens here

  14. lds.sonic.net • Possible causes for rejection • Just about everything on the last slide • Few proper bounces from lds

  15. lds.sonic.net • Logs: /sonic-logs/maillog.lds Jun 18 08:00:38 eth0.a.lds.sonic.net sm-mta[10294]: l5IF0c9N010294: from=<kavan@corp.sonic.net>, size=3013, class=0, nrcpts=1, msgid=<2D1928FE480B98499E46AE0929056FA4C7851D@stingray.office.sonic.net>, proto=ESMTP, daemon=MTA, relay=e.mx.sonic.net [208.201.249.228] Jun 18 08:00:38 eth0.a.lds.sonic.net sm-mta[10295]: l5IF0c9N010294: to=jjc@lds.sonic.net, delay=00:00:00, xdelay=00:00:00, mailer=local, pri=153220, dsn=2.0.0, stat=Sent Jun 18 08:00:39 eth0.a.lds.sonic.net sm-mta[10295]: l5IF0c9N010294: to=jdf@lds.sonic.net, delay=00:00:01, xdelay=00:00:01, mailer=local, pri=153220, dsn=2.0.0, stat=Sent Jun 18 08:00:43 eth0.a.lds.sonic.net sm-mta[10295]: l5IF0c9N010294: to=cmusil@lds.sonic.net, delay=00:00:05, xdelay=00:00:04, mailer=local, pri=153220, dsn=2.0.0, stat=Sent Jun 18 08:00:43 eth0.a.lds.sonic.net sm-mta[10295]: l5IF0c9N010294: to=: eli.caul@corp.sonic.net,kavan@corp.sonic.net, delay=00:00:05, xdelay=00:00:00, mailer=esmtp, pri=153220, relay=mailin-02.mx.sonic.net. [209.204.159.4], dsn=2.0.0, stat=Sent (l5IF0hA6023556 Message accepted for delivery)

  16. lds.sonic.net • When SpamAssassin works: Jun 18 14:12:45 eth0.b.lds.sonic.net sm-mta[32736]: l5ILCj5U032736: from=<aqz2lkxo@kraft.com>, size=3520, class=0, nrcpts=1, msgid=<098i087b.1643738@kraft.com>, proto=ESMTP, daemon=MTA, relay=g.mx.sonic.net [64.142.100.90] Jun 18 14:12:47 eth0.a.lds.sonic.net graymail: jdf sent <098i087b.1643738@kraft.com> "Delois Sarah" <aqz2lkxo@kraft.com> to graymail

  17. spam.sonic.net • Logs: /sonic-logs/mail/maillog.spam Jun 18 14:12:42 eth0.d.spam.sonic.net spamd[2017]: spamd: processing message <098i087b.1643738@kraft.com> for jdf:99 Jun 18 14:12:47 eth0.d.spam.sonic.net spamd[2017]: spamd: result: Y 5 - DKIM_POLICY_SIGNS OME,HTML_MESSAGE,MIME_HTML_ONLY,MONEY_BACK,RAZOR2_CF_RANGE_51_100,RAZOR2_CF_RANGE_E4_51_1 00,RAZOR2_CF_RANGE_E8_51_100,RAZOR2_CHECK,RDNS_NONE scantime=5.0,size=3759,user=jdf,uid=9 9,required_score=5.0,rhost=eth0.a.lds.sonic.net,raddr=208.201.249.231,rport=44935,mid=<098i087b.1643738@kraft.com>,autolearn=disabled

  18. pop.sonic.net • Ports 110 & 995 • Around 500 messages / minute

  19. Where did it go? MTA-level Blocklists SpamAssassin

  20. pop.sonic.net • Logs: /sonic-logs/mail/popper Jun 18 08:01:12 c.pop.sonic.net pop3d: LOGIN, user=jdf, ip=[::ffff:209.204.177.119] Jun 18 08:01:12 c.pop.sonic.net pop3d: LOGIN, dir=/var/spool/mail/03/27/jdf Jun 18 08:01:13 c.pop.sonic.net pop3d: LOGOUT, user=jdf, ip=[::ffff:209.204.177.119], top=0, retr=6786 Jun 18 08:01:13 c.pop.sonic.net pop3d: jdf 209.204.177.119 0.638754 276(Y) 2 (6786), 276 (1490804)

  21. Red Herrings • Not all mail goes through mx • Not all activity on lds is logged • Some “missing” mail isn’t • Blocklists • Aliases • Forwards • Graymail • MUA-level sorting

  22. Finding the Trail • Headers show most of the story

  23. Finding the Trail • A little different after Graymail

  24. Lifecycle of an Email • /sonic-logs/mail/maillog.mail Jun 14 21:54:28 b.mail.sonic.net sm-mta[25018]: l5F4sSsY025018: from=<support@sonic.net>, size=446, class=0, nrcpts=1, msgid=<000c01c7af09$41126700$0cb1ccd1@office.sonic.net>, proto=ESMTP, daemon=MTA, relay=fw.office.sonic.net [209.204.177.119] Jun 14 21:54:28 b.mail.sonic.net sm-mta[25025]: l5F4sSsY025018: to=<spasmcc@sonic.net>, delay=00:00:00, xdelay=00:00:00, mailer=esmtp, pri=120446, relay=mailin-02.mx.sonic.net. [209.204.159.4], dsn=2.0.0, stat=Sent (l5F4sS8F011121 Message accepted for delivery) • /sonic-logs/mail/maillog.mx Jun 14 21:54:28 b.mx.sonic.net sm-mta[11121]: l5F4sS8F011121: from=<support@sonic.net>, size=643, class=0, nrcpts=1, msgid=<000c01c7af09$41126700$0cb1ccd1@office.sonic.net>, proto=ESMTP, daemon=MTA, relay=b.mail.sonic.net [64.142.19.5] Jun 14 21:54:28 b.mx.sonic.net sm-mta[11129]: l5F4sS8F011121: to=<spasmcc@sonic.net>, delay=00:00:00, xdelay=00:00:00, mailer=esmtp, pri=120643, relay=lds.sonic.net. [208.201.249.231], dsn=2.0.0, stat=Sent (l5F4sSju023934 Message accepted for delivery) • /sonic-logs/mail/maillog.lds Jun 14 21:54:28 eth0.a.lds.sonic.net sm-mta[23934]: l5F4sSju023934: from=<support@sonic.net>, size=842, class=0, nrcpts=1, msgid=<000c01c7af09$41126700$0cb1ccd1@office.sonic.net>, proto=ESMTP, daemon=MTA, relay=b.mx.sonic.net [209.204.159.4] Jun 14 21:54:30 eth0.a.lds.sonic.net sm-mta[23945]: l5F4sSju023934: to=<spasmcc@lds.sonic.net>, delay=00:00:02, xdelay=00:00:02, mailer=local, pri=31052, dsn=2.0.0, stat=Sent

  25. Lifecycle of an Email

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