| What about retention-based emails such as | | | | Here we can se the appropriate SMTP codes for a |
| newsletters to your customers or customer service | | | | temporary error and a descriptive text of what has |
| emails? | | | | happened. If the sending email server tries again |
| If you're sending any mass emails to your customers | | | | before the 30 minutes has passed, it will receive a |
| leads, then you should know about Greylisting. | | | | temporary error again: |
| Greylisting (sometimes spelled graylisting) is a | | | | 451 4.7.1 Greylisting in action, please come back in |
| relatively new yet widely used anti-spam method, | | | | 00:15:00 |
| implemented by your customers, that automatically | | | | After the 30 minutes has passed and the sending |
| "drops" all incoming messages coming from your | | | | server tries again, the email will pass and the sender |
| email-address. | | | | triplet will be registered as "whitelisted" for a |
| It's based on the principle that mass email engines | | | | configurable duration (30 days or something like that). |
| don't behave like a normal mail server. Normal mail | | | | That means that subsequent emails from the same |
| servers will, if a temporary error occurs at the | | | | sender to the same recipient will be delivered without |
| receiving end, buffer the email and try again later. | | | | delay. |
| Mass email engines, such as the ones powering | | | | Greylisting is mostly transparent to your customers, |
| common affiliate-systems (sending a newsletter from | | | | besides for a small delay the first time. |
| CommissionJunction, ShareASale etc.) or help-desk | | | | Greylisting is very effective because many mass |
| systems, normally don't have this functionality built in. | | | | e-mail tools will not bother to retry a failed delivery, |
| Greylisting generates a temporary error on purpose | | | | so the email message is never delivered. |
| and waits for the sending server to come back later | | | | If you're using any third party tools to deliver |
| and try to deliver the mail again. A normal server, | | | | messages to your customers/leads, make sure these |
| waits a while, tries again and then succeeds in | | | | tools are greylisting compatible. Our experience |
| delivering the mail. A mass email engine tries one time | | | | working with clients revealed greylisting as the #1 |
| and then the email is lost forever. | | | | reason for low open rates. |
| The greylisting mechanism keeps a database of | | | | SoftwareProjects Email Delivery Platform is fully |
| approved senders, each consisting of sender address, | | | | greylisting compatible, retrying up to 10 times before |
| recipient address and the IP-adress of the sending | | | | marking an email-address as a bounceback. |
| email server. When a new combination is found for | | | | SoftwareProjects offers both a front-end email |
| the first time, a message looking something like this is | | | | marketing service as well as a back-end API-driven |
| sent back to the sending email server: | | | | email delivery engine, allowing you to relay important |
| 451 4.7.1 Greylisting in action, please come back in | | | | messages to customers via our whitelisted platform. |
| 00:30:00 | | | | |