[JAMES-2427] Implement mailets for address verification

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Component/s: Mailet Contributions
• Labels: feature mx
• Assignee: Unassigned
• Reporter: Benoit Tellier
• Created: 14/Jun/18 02:45
• Updated: 14/Jun/18 08:36

Description

We need a class, that tries to send a probe message to a given address.

Depending on the answeres of the other SMTP server, we can deduce if the address exists or not.

We then may implement two mailets:
     - one verifying the recipients of incoming emails
     - one verifying its sender

Here is the page for POSTFIX describing this issue.

Some various concerns:
 - Avoid probing locally handled domains
 - Implement a address cache: do we need persistence for it? POSTFIX does it. We may introduce a corresponding storage API in data-api (Map<MailAddress, IsValid>, basically). Note that cache expiration differs between existing and nonexisting entries.

Idea from @whiteadam proposed on gitter