Notices, email vs certified mail

[Amy Mueller]

Is it ok to send notifications to tenants by email?  I use ezlandlordforms a lot and like that I can get a received and viewed receipt when my tenant opens the email.  Is there any downside to this vs sending something certified mail?

I currently need to send a security deposit accounting statement and with the read receipt feel I have proof if they try to say I didn't send one. 

Secondly is there any reason I can't return the security deposit by EFT?  Zelle vs mailing a check?