Array
(
    [1-grid-mx01.co.za] => 5
    [1-grid-mx04.com] => 5
    [1-grid-mx03.co.za] => 5
    [1-grid-mx02.com] => 5
    [sportwebdesign.co.za] => 0
)

try 1-grid-mx01.co.za:25

<<<
220 spamtitan-filter06.hostserv.co.za ESMTP Postfix

>>>
HELO sportwebdesign.co.za

<<<
250 spamtitan-filter06.hostserv.co.za

>>>
MAIL FROM: <peter@sportwebdesign.co.za>

<<<
250 2.1.0 Ok

>>>
RCPT TO: <peter@sportwebdesign.co.za>

<<<
450 4.2.0 <peter@sportwebdesign.co.za>: Recipient address rejected: Greylisted, see http://postgrey.schweikert.ch/help/sportwebdesign.co.za.html

>>>
RSET

<<<
250 2.0.0 Ok

>>>
quit

<<<
221 2.0.0 Bye

Array
(
    [gmail-smtp-in.l.google.com] => 5
    [alt1.gmail-smtp-in.l.google.com] => 10
    [alt2.gmail-smtp-in.l.google.com] => 20
    [alt3.gmail-smtp-in.l.google.com] => 30
    [alt4.gmail-smtp-in.l.google.com] => 40
    [gmail.com] => 0
)

try gmail-smtp-in.l.google.com:25

try alt1.gmail-smtp-in.l.google.com:25

try alt2.gmail-smtp-in.l.google.com:25

try alt3.gmail-smtp-in.l.google.com:25

try alt4.gmail-smtp-in.l.google.com:25

try gmail.com:25

Error: Could not connect to a valid mail server for this email address: peter@gmail.com