Sender Emails containing a plus + are not accepted as valid

Sender Emails containing a plus + are not accepted as valid

We use sender email addresses containing a plus +.

But email addresses containing a plus are not accepted as valid email address by the Zoho Campaign form, although they are valid and working email addresses.

Please respond on how long it takes to change this, as we want to start using Zoho Campaign productively by the end of this week.

I report this as a problem as afaik such isn't documented as a no-go soft factor in email permission marketing. Maybe I've overseen something, I happily to receive explanations.