> A - Verify MAIL FROM address

the simple verify is no longer usable, as more and more servers disable it.

all MXs should disable it.

but for verification:

RCPT TO:<[EMAIL PROTECTED]>

... works just as well as VRFY command.

there is a new smtp message 252 "try sending" "valid email adresse foprmat"
or similar text. (i guess imail does not a complete mail from: and rcpt to:
cycle to determin a valid sender?

after the MX's response to RCPT TO:, it's perfectly valid for the SMTP client to QUIT


> B - Perform reverse DNS lookup for connecting server

this will always fail for a mailserver connected to a dynamic ip-adress pool
like most dsl-providers (at least in germany) use.

mailservers on dynamic IPs are pretty useless. It's a good practice to block any mail to your MX from dynamic IPs.


Len

_____________________________________________________________________
http://MenAndMice.com/DNS-training : Denver; NYC; San Jose
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