SMTP Support

[maaslalani]

Adds SMTP support for pop.

Configured by environment variables:

export POP_SMTP_HOST=smtp.gmail.com
export POP_SMTP_PORT=587
export POP_SMTP_USERNAME=...
export POP_SMTP_PASSWORD=...

If @gmail.com is the suffix of the POP_SMTP_USERNAME then we will automatically set the default of the HOST and PORT to smtp.gmail.com and 587.

[meowgorithm]

I believe port 587 is now the de-facto standard SMTP port, so perhaps it's worth defaulting to that regardless of whether or not gmail is being used?

[maaslalani]

I believe port 587 is now the de-facto standard SMTP port, so perhaps it's worth defaulting to that regardless of whether or not gmail is being used?

Ah nice, good point. Will make it the default 👍