flake8: rename loop variable in 'for sendto in sendto:' Flake8 reported 'B020 Found for loop that reassigns the iterable it is iterating with each iterable value.' Renamed loop variable to to_addr. There is a similar construct with a loop over bcc_sendto with a 'bcc' loop variable. So I assume the loop varaible can be chnaged w/o issue. Codecov shows all the affected lines are being tested and the tests I ran with testmon that should cover that code all passed. We shall see if a full CI run passes.

# human timezones
pytz
# indexer
Whoosh
# xapian is also installed
# extra database support
psycopg2
mysqlclient
redis
# encryption
gpg
# java web tokens
PyJWT
# extra HTTP compression methods
Brotli
zstd
# jinja2 template engine
Jinja2