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5.1.7 Invalid sender address syntax when asking for notification

user1366614
user1366614
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when sending mail with notication to provider KPN I get an 5.1.7 Invalid sender address syntax when sending without notification of recieving no problems what to do?

when sending mail with notication to provider KPN I get an 5.1.7 Invalid sender address syntax when sending without notification of recieving no problems what to do?

Chosen solution

I heard about an undocumented solution: using mail.planet.nl, port 25, ssl, no username (!) all working again

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user1366614
user1366614 Question owner
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and I checked my sent mail header looking at the source of the message: there is no "Return-Receipt-To" ??? From - Mon Dec 12 06:22:20 2016 X-Mozilla-Status: 0001 X-Mozilla-Status2: 00800000 X-Mozilla-Keys: To: xxx@xxxxx.nl From: bbb <bbbbbb@planet.nl> Subject: test Message-ID: <f75a421a-b35f-4852-20de-316c3bf2f816@planet.nl> Date: Mon, 12 Dec 2016 06:22:19 +0100 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:45.0) Gecko/20100101 

Thunderbird/45.5.1

MIME-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit

user1366614
user1366614 Question owner
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Chosen Solution

I heard about an undocumented solution: using mail.planet.nl, port 25, ssl, no username (!) all working again