Message has lines too long for transport Error in Outlook

[Mapachio]

So I got a WHM hosting service in a dedicated hosting.

When my clients use OUTLOOK to send emails they sometimes got the "Message has lines too long for transport" error. I send a ticket to CPANEL and they told me this:

Looking at your server, you have Magicspam setup on your server. This service is not controlled by cPanel but does create custom transports, which is where the problem resides.

[19:44:19 azathoth root@94525197 ~]cPs# grep -i "Message has lines too long for transport" /var/log/exim_mainlog | head -n2
2023-01-23 08:55:38 1pJxIP-000DjV-7t ** jchambir@hotmail.com R=remoteserver_route T=mailchannels_smtp: message has lines too long for transport
2023-01-24 16:58:33 1pKRJJ-0007US-Td ** alonso.vargas@sullair.com.pe R=remoteserver_route T=mailchannels_smtp: message has lines too long for transport

I see no message length has been added to these transports. Please look at the following article with your system administrator and include that in your custom transports.

"Message has lines too long for transport" with custom routers in v102+ : https://support.cpanel.net/hc/en-us/art ... s-in-v102-

I am confident the knowledge shared in the above article will guide you towards solving the issue you have outlined in this request. Would you please review the article and let me know if you have any outstanding questions or concerns? It’s been a pleasure working with you on this issue, and I hope you are satisfied with the experience!

So I need to know where to change this. A lot of clients are having problem with this.

[magicspam]

Hello Mapachio,

Based on the provided information, the grep command reveals that the "Message has lines too long for transport" error is associated with the MailChannels transport (T=mailchannels_smtp) rather than with the MagicSpam transport. As such, it's rather peculiar that cPanel jumped to the conclusion that it is related to MagicSpam.

However, we should still be able to provide you with some guidance on how to go about resolving this issue. We checked the cPanel documentation and see that there is an Exim configuration that can be changed which may resolve the reported issue:

WHM Panel >> Exim Configuration Manager >> Basic Editor >> Maximum line length for SMTP transports

This Exim Configuration is set to 2048 by default, so you will want to double it to 4096 and monitor the system to see if the issue is resolved. If the issue still occurs, then double the value again and repeat the process until the issue no longer occurs.

Please refer to this cPanel Support Documentation for more information.

We hope this information is helpful to you.

Thank you.