Add the ability to pause emails

[sudar]

• Add a new setting to pause/unpause emails
• When email is paused it won't be sent, but stored in email log

TODO from #224

• If the email is just paused (see Add the ability to pause emails #220 ) then add a message that says Email is paused

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Attached PR(s)

• Pause Emails :: Implement Settings page #239

[mariadanieldeepak]

@sudar,

I see two ways to pause the emails.

1. Using phpmailer_init hook

We could use this hook and throw an error.

Cons: If there are other plugins that are monitoring for email sent status, then Email Log plugin will give false data to those plugins.

2. We could override the global $phpmailer

We can create a class that extends PHPMailer class and fake the send() method.

Cons: I don't see a Con here.

Kindly share your thoughts on which route would your prefer.

[esudalaimadan]

@sudar I have queries on requirement as well as implementation:
Queries on requirements:

1. Are we going to pause all emails sent by WordPress or allow the user to pause selective emails?

Queries on implementation:

1. I have gone through disable emails plugin and it is pausing all emails sent via WordPress.
2. In stackoverflow, few people said, clear all the recipients then wp_mail won't send emails. But I think that is not the proper way to disable emails.