don't parse addresses with invalid domains

Per RFC 2822, domains like ".domain.com" or "domain..com" are not valid.

```
# RFC 2822
dot-atom        =       [CFWS] dot-atom-text [CFWS]
dot-atom-text   =       1*atext *("." 1*atext)
```

Domains should be a domain_text element followed by zero or more
domain_text elements prefixed with "."