PureEngage On-Premises

According the release notes for WDE 8.5.114.08 there was an improvment regarding "Improved email address format validation. This improvement ensures that 'To', 'CC', and 'BCC' email addresses are correctly entered when the agent attempts to send the email."
In WDE 8.5.117.18 and even the last one, 8.5.117.26 the agent is still able to enter a not RFC822 compatible address like "xxx.test@test.com.au." (notice the last point after "au", which is not RFC822 compliant.

In WDE options there is an object "expression.email-address" only this refers to chat and sms transcripts.
De default value is \w+([-+.]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)* but according online regular expression builders the above mention email addres is still valid.
A more appropriate reg ex could be: ^[a-zA-Z0-9.!#$%&'*+/=?^_`{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*$ which exclude above mention email address.

Is there any standard option to validate email address formats, except to add a check in the routing?

Email address xxx@yyy.xxx.zzz is valid based on RFC822.

yes, that true, but when the agent put a dot behind your case ==>  "zzz." than it should not be RFC822 compatible. In our case WDE is still agree with the last dot after "zzz."

I think on WDE is not possible to check email address format (maybe I am wrong - to make sure check that with Genesys Care). My opinion is that the email will not be sent at all as the ESJ will not allow it due to the RFC822 incompatibility. So, these emails you can easily move to some target (workbins, etc.) and process them later.