Steps to reproduce:

1. Setup "Alert" "Media types" with "Office365 Relay"
2. Configure "Email" with any domain @domain.com.br (TLD that are not just .com)
3. Update configuration and MX/SMTP Server get misspelled.

Result:
SMTP server: "example.com-br.mail.protection.outlook.com"

Log entry

failed to send email: Couldn't resolve host name: Could not resolve host:  domain.com-br.mail.protection.outlook.com

Expected:

SMTP server: "domain-com-br.mail.protection.outlook.com"

There's a "." (dot) after domain when should be "-" (hyphen)

 domain-com-br.mail.protection.outlook.com

Fix: (WARNING)

I didn't spent a lot of time checking the code. I'm not a programmer, this change is not the best solution!!  But I was able to identify the error.

zabbix/app/controllers/CControllerMediatypeUpdate.php => line 122

zabbix/app/controllers/CControllerMediatypeUpdate.php => line 132

$formatted_domain = substr_replace($domain, '-', strrpos($domain, '.'), 1);

Changed to:

$formatted_domain = str_replace('.', '-', $domain);