[Asrg] Verizon's asymmetrical anti-spam causing problems

["Peter Kay" <peter at titankey.com>]

Title: Message

Has anyone noticed/experienced Verizon's asymmetrical anti-spam email address verification?  After you connect to their mail servers and send the MAIL-FROM / RCPT-TO commands, before they come back with an OK, they do a reverse check of the MAIL-FROM address to see if it's valid and if not, return a fatal error.

 

While Verizon is certainly not the only ISP doing address verification, and I'm personally in favor of the approach, what I object to is that their approach is not symmetrical, meaning that if another server (e.g. Mailsender.com) were to employ the identical method that Verizon does, neither Verizon nor Mailsender.com would be able to send each other email.

 

The reason for this asymmetry is that the Verizon probe addresses are in the form of antispamxxxx at west.verizon.net or something to that effect where xxxx is a 4 digit number. So if Mailsender.com used probes like antispamxxxx at east.Mailsender.com you can see the problem, that being:

 

A. Mailsender sends email to Verizon.

B. Verizon holds the connection and attempts a probe to Mailsender.

C. Mailsender holds the connection and attempts a probe to Verizon.

D. (does this create an infinite loop?)

E. Verizon's probe fails.

F. Mailsender's probe fails.

G. Legitimate email is never sent.

 

Has anyone else had problems with this? I did quick check on their site and didn't find anything.

 

Have there been any BCP or equivalent on email address verification? I haven't easily found any.

 

Peter Kay

Titan Key Software

Unique spam-bouncing technology

 

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