External email address in AD- General - Email field

Hi,
We have a hybrid environment with students having mailboxes on Exchange Online and staff mailboxes on Exchange on-premises. Parents Active Directory user accounts are not mail-enabled or mailbox-enabled.
We need to populate Active directory with parents email addresses for integration purposes with other systems. Do you envisage any issues with using AD E-mail field to enter external email addresses?
Thank you for your help.
Svetlana