I want to give users to enter an E-mail address to which my flow will send an E-mail later. Is there a standard way to check if the address (one or multiple) is valid?
If you have them enter it in Powerapps then you can use isMatch() to check it against a Regex expression. But Regex support isn't available in Flow. How were you planning to have the users enter the Address(es)?
If you are using a PowerApps form take a look at the PowerApps IsMatch function. YOu can use it to evaluate a field using Regex. That's probably the best way to test email addresses.
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