Sagacious Himself — brevity in circumlocution: never blague — suffering genius

December 2, 2013

@ cretinous admins of reseller isp email: SPF can accept dDNS fqdn to acomodate dynamic IP address of email clients using another ISP

Filed under: all these — Sagacious Himself @ 2:10 pm

Someone’s email service was sold to an apparently dim bulb.  Now someone’s emails are being bounced by recipient systems.  Someone uses big name ISP, but their email domain was of a different small local DSL reselling ISP whose admin was barely capable of keeping up proprietary email server.  Smalltime ISP sold company to a slightly larger conglomerate.  Slightly larger admin is even more feckless than DSL reselling ISP having poorly configured SPF and other email policies.

Someone needs to be able to continue emailing from:  office ISP, residential ISP, mobile ISP.

Someone has a few options that feckless conglomerate admin could implement to allow someone’s difficult to change email address continue to function.  Changes to SPF TXT-record:

  1. add FQDN provided by someone:  dDNS (dynamic DNS A-record for someone’s dynamic IP address)
  2. someone could purchase a block of static IP address from ISP (ISP will not sell one IPa to residential clients)



PRO: is least costly to someone and in no way technically challenging for feckless conglomerate admin.
PRO: suitable for business ISP and residential ISP

CON: DNS negative caching expiration (errantly refereed to as DSN propagation).  When IPa changes some few emails will be rejected as differential cached value and current value reach equilibrium.  Most problematic
CON: not suitable for mobile ISP (without vast hackery to hold IPa, chew battery).  VZW CGN extra-problematic.


Other than SPF options

  1. conglomerate un-disable SMTP AUTH for client



VZW CGN bane to Himself (PDF)

^ within verizon wireless document a verizon admission of what I’ve alleged: some handsets had [public] routable IP addresses (IPv4) until some didn’t.  (me and several dozen people with vzw savvy to the issue (vpn or sip)) — wherein I provided free re-education to verizon agents.  Will VZW inflict ULA (RFC 4193) with IPv6?  Sure as they’re demonstrably SIP-hostile.



someone could purchase a block of static IP address from ISP (ISP will not sell one IPa to residential clients)

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