| Sanford Whiteman 2007-05-03, 1:20 am |
| > Unable to verify sender address
Self-explanatory error, to a degree. The destination mailserver is
checking the validity of your MAIL FROM address. The most primitive such
check simply checks if your sender domain exists in the public DNS; a
deeper check checks for an MX record; and the deepest such verification,
called a Sender Address Verification (SAV) callout, actually connects back
to _your_ MX to determine whether your full sender address accepts mail.
SAV checks can be flawed in several common scenarios, but unless you
expect that you _should_ be failing SAV at this time (for example, if your
MX is down), you should keep looking for the root of the problem on your
side.
Do you see a hit in your logs from the remote server back to your MX
during the session (that's what a callout will look like)? If so, how
does your server respond?
What's the exact MAIL FROM address of these messages? Can you verify it
at outside DNS servers?
--Sandy
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