Webtop - send mail issue with Samsung GSM

NethServer Version: NS8
Module: Webtop

Hello,
I switched from SOGo 5.11 to Webtop 5.26.1 webmail. Everything was OK with SOGo.
After installing Webtop and configure it, I have issues to send mails from my Samsung mobile phone
Webmail is working like a charm with Nextcloud integration.
EAS synchronisation is also working fine on the GSM.
I use the Samsung email app. This is only happening if I want to send mails.

I also read the note:
On some Android releases (notably Samsung), the User name and Domain must be entered in the same line. In this case, leave blank the field before the backslash character \ , and enter the user name in the following format: \goofy@nethserver.org

Here the message in the webtop log file:

2024-10-16T12:02:49+02:00 [1:webtop2:z-push] 127.0.0.1 - xxx@yyy.org 16/Oct/2024:10:02:48 +0000 "POST /Microsoft-Server-ActiveSync" 200
2024-10-16T12:02:49+02:00 [1:webtop2:apache] 10.0.2.100 - - [16/Oct/2024:10:02:48 +0000] "POST /Microsoft-Server-ActiveSync?Cmd=Sync&User=xxx%40yyy.org&DeviceId=SEC1601E740ED5A0&DeviceType=SamsungDevice HTTP/1.1" 200 819494
2024-10-16T12:02:55+02:00 [1:webtop2:z-push] sendmail: can't connect to remote host (127.0.0.1): Connection refused
2024-10-16T12:02:55+02:00 [1:webtop2:z-push] 127.0.0.1 - xxx@yyy.org 16/Oct/2024:10:02:55 +0000 "POST /Microsoft-Server-ActiveSync" 200
2024-10-16T12:02:55+02:00 [1:webtop2:apache] 10.0.2.100 - - [16/Oct/2024:10:02:55 +0000] "POST /Microsoft-Server-ActiveSync?Cmd=SendMail&User=xxx%40yyy.org&DeviceId=SEC1601E740ED5A0&DeviceType=SamsungDevice HTTP/1.1" 200 15

Does anyone have any idea what might be causing this problem?
Thank you for your help.

Just one more information.
Sending mails from the web interface is OK ;-).

Hello,
Is there someone who can help me with this problem?
Is there someone else who has the same problem?
Thank you.

As general advice, use IMAP and SMTP for the mail, not ActiveSync.

Open Source implementation of ActiveSync is not great on the mail part.

Let’s see if @lucag has a better advice.

@giacomo
Many thanks for your advice.
@lucag
Do you have a better advice for me?
It would be great if I could use the EAS with Webtop.
Many thanks in advance for your help.