Make sure a trailing brackets corresponds to a leading one

[manu0401]

This fixes the case where the sender e-mail address is [email protected]> Without this fix, OpenDMARC parses the domain as example.net> and skip DMARC processing since there is no policy for the domain.

Unfortunately, the MTA or MUA tend to fix the trailing bracket on their own, letting forged e-mail passing through to user mailboxes.