Sorry to hear that; I think that maybe you should enable in your e-mail configuration the sent from other email addresses.
For example in gmail we had to enable in our notifications@mydomain.com preferences a secondary account to send email as support@mydomain.com

Hi Xavier,
you can set it as Default System Email in email > settings.
Alternatively, department can set its own Email Address which will override the system default

Cheers ?
Nicoletta

Hi @Chabi0167,

we solved this situation with this configuration:
• set notification@mydomain.com as Default MTA in Admin Panel -> Emails -> Settings
• allow Header Spoofing in notification@mydomain.com configuration
• set support@mydomain.com as outgoing email address

Hope it helped!