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sent email error
Problem reported by Somkiat Apisuttimaitree - 7/29/2024 at 8:43 PM
Submitted

Sent an email through Outlook and it bounced.

This is the mail system at host antispamawn01.thaicloudsolutions.com.

I'm sorry to have to inform you that your message could not

be delivered to one or more recipients. It's attached below.

For further assistance, please send mail to postmaster.

If you do so, please include this problem report. You can

delete your own text from the attached returned message.

The mail system

: SMTPUTF8 is required, but was not offered by host

203.146.246.165[203.146.246.165]

: SMTPUTF8 is required, but was not offered by host

203.146.246.165[203.146.246.165]


smartermail latest update
Andrew Barker Replied
7/30/2024 at 5:21 PM
Employee Post
The SMTPUTF8 extension allows servers to send messages that include unencoded UTF8 characters in the MIME headers. This extension is necessary to support Email Address Internationalization (EAI).

When SmarterMail sends a message, it parses the remote server's EHLO response to determine if it supports SMTPUTF8. Based on that, SmarterMail builds the outbound message, applies DKIM signing, and sends the message.

Due to security features like DKIM signing, the RFCs state that a message cannot be downgraded except by the originating server. This can create a situation where SmarterMail sends the message to a gateway that supports SMTPUTF8. The gateway then tries to send the message to a server that does not support SMTPUTF8. Because the gateway is not the originating server, it cannot downgrade the message and must generate a bounce message which it sends to the original server.

We are discussing possible changes that can be made in SmarterMail to minimize the occurrence of bounces related to SMTPUTF8 support, such as a way to disable use of SMTPUTF8 when sending to a gateway.

Andrew Barker
Lead Software Developer
SmarterTools Inc.
www.smartertools.com 
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