Send response to 550 and 552

[ThomasTJdev]

PR with own PR from arithmetric#127 .

This PR consist of two main elements - auto response on:

• SMTP 550 - no recipient found
• SMTP 552 - mail size exceeds 10 MB

550 - no recipient found

When a person is sending an email, and global catch (@example.com) is not enabled, the email will just disappear - neither the sender nor the email-admin will be notified. If the new "notify"-config is enabled, the sender will be informed, that the recipient does not exists.

Config

notifyEmail: "MAILER-DAEMON@example.com",
notify550: true,

Response

An error occurred while trying to deliver the mail to the following recipients: test@example.com

Your email was rejected. The email address was not found. Please check the receiving email address.

SMTP Reply Code = 550, SMTP Status Code = 5.1.1

552 - mail size exceeds 10 MB

Another problem is when the mail size exceeds AWS's limit on 10MB. This will also fail silently (arithmetric#97, arithmetric#124) - not notifying either the sender or the email-admin. If the new "notify"-config is enabled, the sender will be informed, that the recipient does not exists.

Config

notifyEmail: "MAILER-DAEMON@example.com",
notify552: true,

Response

An error occurred while trying to deliver the mail to the following recipients: test@example.com

Your email was rejected. Please ensure that the size of your mail is less than 10 MB.

SMTP Reply Code = 552, SMTP Status Code = 5.3.4

[ThomasTJdev]

Just to inform those of you coming from original branch - this PR has been merged and it works perfectly!