For enlightenment?

CDs are rated for 10–30 years, Blurays for 50–80. YMMV with cheap low quality disks, of course.

Steel decays pretty quickly. The most durably data storage medium we’ve figured out is still ceramics

Different providers have different spamfilters, different rules regarding html mails, attachment file size, use of tls, policies regarding exspired certificates, and might have different log in procedures, so yes, if there are problems the question which providers are involved.