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2 Messages

Sat, Aug 18, 2018 6:23 PM

Please help with IP Address Blocking

We are a web-hosting company and are having problems sending emails to a client of us with a email address, from 2 different email addresses and two different IPs

    host []
    SMTP error from remote mail server after MAIL FROM::
    553 5.3.0 alph165 DNSBL:ATTRBL 521< >_is_blocked.For assistance forward this email to

    Same happens when sending emails from another IP -

    We have very strict policies against spam and restrict a lot our customers from sending newsletters,  so there should be no reason for being blacklisted... we are not on any RBL

    Would you please unblock those 2 IPs for us, and

    We would appreciate that since need to regularly contact our customer at an email address    

    Pls advise



Accepted Solution

Official Solution

Brand User

New Member


121.2K Messages

2 years ago

Hello, @Harpwro
We understand how much of a hassle this could be. You would need to reach out to report your complaint to, Someone will get back to you in help get your IP addresses unblocked. Charles, AT&T Community Specialist

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