Remove %e formatting verbs

%e is not valid for formatting error values:

> %e	scientific notation, e.g. -1.234456e+78

Instead, use %w when using fmt.Errorf (for error wrapping) and
%v when using log.Printf (%w is not valid in that context).

Configure server to manage mail queue

This also sets up the recovery function for webhooks, so we get emailed
when we panic during a webhook query.

Encrypt outgoing emails

Sign outgoing emails

Make worker logs less loud

Expand context for work queues

email: remove leftover debug code

Add email work queue