[mailscripts] less secure options for imap-dl

[David Bremner]

I'm currently using davmail on my workstation as a proxy to access my
uni exchange server. Setting up davmail with letsencrypt SSL certs seems
like overkill (especially on a machine without a public IP
address). Unfortunately imap-dl does not support self-signed
certificates afaict, nor the SimpleIMAPRetriever of getmail.

I might or might not find time to hack something in myself (depending
how on how getmail6 treats me), but I thought I'd find out if you were
receptive to adding the ability to either skip ssl or allow self-signed
certs (assuming it's doable while still using the python stdlib).

d