The OP has really boned himself by ignoring the notice to appear that he admits he was mailed. In California, the court may try you in absentia if you fail to appear. (CVC 40903) Once you've been tried and found guilty, the court may impose a fine. That order can include a date by which the fine must be paid (CVC 42003(a)). If the guilty party fails to pay by that date, the court may place a hold on the party's drivers license. This hold is not released until the fine is fully paid. (CVC 40509.5(b))
The Vehicle Code governs the rules around AETS Notices to Appear. There is a proof of service requirement, but not one that requires certified mail. (CVC 40518). This also requires that the notice was mailed within 15 days of the date of the infraction.
The Cal Code of Civil Procedure covers the requirements for proof of service. For service of notice of a court hearing CCP 684.220 allows, among other things, proof of service by mail, proof of service by written admission of the party served, and testimonial evidence of proof of service. First class mail is standard for service by mail, in accordance with CCP 684.120. The exact requirements for the contents of the certificate or affidavit is given by CCP 1013a.
It doesn't work that way, unfortunately. The OP could have appealed his conviction after final judgement (PC 1466), but he only has 30 days to do so. (CRC 8.902). Since he's way outside of the 30 day window the only solution here is to either attempt to appear in court to resolve the matter, or pay the fine. If the hold is placed in accordance with 40509.5(b), the fine has to be paid. If it's 40509.5(a), it's possible to set a court date and have a certificate sent to the DMV that will release the hold.

