Use tls options in sockopts for ssl connection

[alappe]

While trying to make bamboo_smtp work with the smtp server of domainfactory (df.eu), I found I needed some options handled differently. While I'm not into the topic taming the ssl beast, I wanted to share it and maybe collect some feedback if this is wrong on my end or should fully/partly merged into bamboo_smtp.

Using it with (username/password/hostname omitted):

adapter: Bamboo.SMTPAdapter,
server: "sslout.df.eu",
port: 465,
tls: :if_available,
retries: 3,
auth: :always,
ssl: true,
tls_verify: :verify_peer,
tls_server_name_indication: "sslout.df.eu",
tls_depth: 10,
tls_log_level: :debug,
tls_cacertfile: CAStore.file_path()

It seems to me that gen_smtp (v1.2) gave up on collecting/validating the tls options (gen-smtp/gen_smtp@3cfd421) and is simply passing sockopts to ssl:connect() while using tls_options when using STARTTLS. If I read this right it might be easier to do the same, skip the validation of known tls-related config keys/values, move the configuration to tls: [ verify: :verify_peer, … ] and pass this to gen_smtp. But this would be a breaking change…

Any opinions?

[DerTim1]

Reviewed and tested the changes. We also need the ability to set server_name_indication to work again with smtp.office365.com (Server-Name-Indication: outlook.com).

👍