rdisp/vbmail is a SAP Parameter attribute which is used to control Send mail in case of an update error information. This is available within R/3 SAP systems depending on the version and release level.
Below is the standard documentation available and a few details of the attributes values .
The user is informed of update errors by sending an express mail. These
mails can be deactivated:
Parameter value = 1: A mail is sent.
Parameter value = 0: No mail is sent.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.