User when he sent single email able to receive it but scheduled emails are not going through

[amahmud01]

Hello,

trying to understand this issue my colleague is facing, he is relaying from a server to send scheduled emails through ESA, the werid thing when he send a test email he is able to receive it in his inbox but when he schedule through his script it doesn't go through, tried to telnet from the server and he is getting below error.

 

need you help please 

[amahmud01]

i wonder if any one

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@amahmud01 wrote:

Hello,

trying to understand this issue my colleague is facing, he is relaying from a server to send scheduled emails through ESA, the weird thing when he send a test email he is able to receive it in his inbox but when he schedule through his script it doesn't go through, tried to telnet from the server and he is getting below error.

 

need you help please 

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faced this kind of problem 

[ppreenja · Accepted solution]

Hi,

The error occurs usually due to issue on the mail client site because it sends binary in 8bit format:

Content-Transfer-Encoding: binary

RFC 821 restricts mail messages to 7-bit US-ASCII data with 1000 character lines.

Some background information about encoding:

You may observe that an email message with a binary attachment appears to be much larger in size when viewed via the mail_logs compared to the size of the binary attachment. This is because binary files in attachments are encoded before the email message is delivered to an MTA. The most popular are base64 and uuencode. The goal of encoding is to accurately represent 8-bit characters within the 7-bit limitation of SMTP.

With that said, the mail client of the user is not using proper encoding. Because of that, the appliance is unable to understand the communication from the Exchange server sending an un-encoded message which is causing the bad SMTP commands. You can investigate further on the mail client site and ensure that all messages are properly encoded e.g. using base64.

Also, I was able to find the below article which might be able to assist you further in which you can make changes in the maximum number of message header lines in listenerconfig to avoid similar error:

https://www.cisco.com/c/en/us/support/docs/security/email-security-appliance/118495-technote-esa-00.html

I hope the above information helps.

Cheers,
Pratham