SymptomsWhen you try to add specific "MX" records in DNS records for domains, for example, records where "Mail exchanger" is set to something like this ...
"Error at the first position. Mail exchanger host name must contain latin characters, digits, hyphens and points only. It should be valid domain name."
The error is shown for records with the "-" symbol ("tst-test.com") or where there is a character separated by dots that is no longer than 1 symbol: aaa.f.com, s.test.com, 1.com, etc.
CauseThere is a new setting in the Provider's Control Panel that was introduced as part of POA 5.0: Allow using of IP address in MX records.
The default value of the setting after an upgrade is "Enabled" to preserve the old behavior. If the provider changes the setting to "Disabled," the error described in the "Symptoms" section may be observed because of an incorrect default validator for MX records.
Note: To check the setting's current value, switch to the following location: "Top » System Director » Configuration Manager » System Properties."