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johnnyquad
Level 7

#< #5.0.0 smtp; 510 Did not receive the expected protocol response.> #SMTP#

Can anyone tell me what this actually means: #< #5.0.0 smtp; 510 Did not receive the expected protocol response.> #SMTP#

I keep seeing this attached to "Delivery has failed to recipients of distribution list:" message that hits my administrator mailbox. The message is being generated by one of my Ironmail server.

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3 Replies
ijahnke
Level 11

Re: #< #5.0.0 smtp; 510 Did not receive the expected protocol response.> #SMTP#

It most likely is caused by the message size. This is a known issue with IronMail where it does not properly handle or report the "Message Size Exceeded" error as a permanent failure.

You can check the maximum size the recipient server accepts by doing a simple telnet to their server and then typing EHLO mydom.com:

telnet <ip address/hostname of recipient server> 25

ehlo mydom.com

Example:

telnet mail.mydom.com 25

Trying 10.10.10.10...

Connected to mail.mydom.com.

Escape character is '^]'.

220 SMTP Proxy Server Ready

ehlo mydom.com

250-ESMTP Server Ready

250-SIZE 10485760

250-DSN

250-STARTTLS

250 TLS

If this isnt the case, then we would need to see a packet capture to determine what invalid response we are seeing.

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johnnyquad
Level 7

Re: #< #5.0.0 smtp; 510 Did not receive the expected protocol response.> #SMTP#

What version of the code is this a known issue in?  Has this been fixed in a recent code upgrade?

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ajclements
Level 11

Re: #< #5.0.0 smtp; 510 Did not receive the expected protocol response.> #SMTP#

It the problem you are seeing is the size limit issue, it was fixed with 6.7.2 HF6.  But the size restriction is only one of many things that can cause the error.

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