Electronic registered mail with reception acknowledgement is regulated by the law and carries a higher legal guarantee than paper registered mail with reception acknowledgement.
ERM vs. Email
Sending a simple email does not carry sufficient legal guarantees.
An email already has legal value (you can prove that an email has been sent to a specific email address and you can prove to be the owner of that given email address); but only the sending can be proved, not the reception.
Neither the reception of an email on the server (inbox), nor its opening by the recipient (supposing you can prove the email was received by the server) can be proven.
As a consequence, when sending a simple email, you cannot prove its reception but only that certain content has been sent to a given email address on a given date.
However, in the case of a legal dispute, the sender needs to be able to give proof of the sending, and this may induce very high expenses for IT expertise services.
ERM vs. Certified Email
Sending a certified email may help to overcome some issues, but it is not enough either.
A certified email simply adds time-stamping (content, attached documents, email address of the sender, email address of the recipient and date of the sending) without giving proof that the email was actually received.
Like a simple email, it lacks the proof that the server received the email and proof that the email has been opened (if received by the inbox).
In brief, with a certified email the sender won’t need to pay for IT expertise services in order to prove that the email has been sent, but there won’t be any proof that the email was actually received.
ERM vs. Email with Reception Acknowledgement as proposed by some email services (such as Outlook)
Once again, an email with reception acknowledgement does not offer complete legal guarantees.
The only additional benefit compared to a simple email, is that the recipient can send the proof of reception acknowledgement to the sender.
However, sending the proof of reception acknowledgement requires that the recipient has opened the email and thus wished to do so!
The reception acknowledgement for a simple email has no legal value.
The ERL is the only 100% digital means of communication that has a guaranteed and recognized legal value, all the way through.