Email Marketing Server ESD Cannot Send Emails - Error 501 5.1.7 Bad sender address syntax (Doc ID 2023027.1)

On :  8.1.1.5 SIA [21229] version, Email Marketing Server

Newly installed ESD is not sending emails but coming back with soft bounces:

ERROR
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2015-05-11 16:17:25,269 [QueueReader-0-bounceQueue] DEBUG2 BounceProcessor row: [11-JCOXXX, Soft, Protocol Problem]

This appears to be cause by "501 5.1.7 Bad sender address syntax":

2015-05-11 16:17:05,878 [SMTPTalker-7] DEBUG SMTPTalker Connect to local MTAs (192.xxx.xx.xx/192.xxx.xxx.xx) took 47: 220 postmatix.xxx.xxx.xx ESMTP Postfix
2015-05-11 16:17:05,909 [SMTPTalker-7] DEBUG2 MailingState Failing [a.xxxxx@xxx.xx, [Account Location=,First Name=ΠΑΝΑΓΙΩΤΗΣ,Camp Con Id=11-JCOxxx,Last Name=ΝΤΑΚΑΣ,Cellular Phone #=+1(693) xxx-xxxxx,Contact Id=1-ASX-1xxx,Account=,Segment/List Name=EMAIL SEGMENT J,Job Title=ΔΗΜΟΣΙΟΙ ΥΠΑΛΛΗΛΟΙ ΑΛΛΟΙ,Source Code=37-117014xxxx,Fax Phone #=,Prospect Id=,Work Phone #=+1(224) xxx-xxxx,Middle Name=ΓΕΩΡΓΙΟΣ,Email Address=a.xxxxxx@xxxx.xx,Current Date=11/05/2015,Home Phone #=+1(224) xxx-xxxx,M/M=]]: 501 5.1.7 Bad sender address syntax(2)

Changes

Cause

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