You seems got this error at Roundcube or Horde.
Here is explanation how it works:
Supposedly you’re trying to send message with an attachment file 44M
And you have the message_size_limit set in 50M as explained here
And you will not be able to send such message because attachments in a message are encoded by base64
It means your message will be by 30% bigger than expected, please see below calculation
You cannot send such message due to the limit in 50M, so you need either rise message_size_limit or upload and share your attachment to services like Gdrive/Dropbox/etc… Read the rest
Make sure hostname is good:
Did you run /scripts/upcp –force? If not do it.
If you run it already, run it again as I got this fixed after the second run.
If still not working:
rm -fv UpdateHostname\:USERNAME
where USERNAME is cPanel username.… Read the rest
cPanel’s Horde has “Inline HTML” is disabled by default
The error you probably got:
This message part contains HTML data, but inline HTML display is disabled.
View HTML data in new window.
Convert HTML data to plain text and view in new window.… Read the rest
By default HTML viewing message for Horde is disabled
To enable edit the following file
And change the following line
$mime_drivers['imp']['plain']['inline'] = false;
$mime_drivers['imp']['plain']['inline'] = true;
Syntaxis has been little bit changed, so now you need to update the following section in /usr/local/cpanel/base/horde/imp/config/mime_drivers.php… Read the rest