List hygiene is a best practice in order to maintain a high sending reputation, deliver your messages more quickly and keep high deliverability rates.

Sending messages to inboxes that constantly refuse them affects your reputation as a sender in various ways:

When sending a message to a list triggers a high number of bounces, it means that the list is "dirty": it contains old, incorrect, or otherwise unreachable addresses, which simply should not be there. Maintaining your list "clean" is extremely important: it affects your reputation as a sender, and it also affects your ability to properly analyze the overall performance of your campaigns, ensuring that what you are looking at are accurate statistics. It also impacts your total delivery time, since you are (unnecessarily) sending messages that will not be delivered.

With regard to your reputation, consider that Internet Service Providers (ISPs) keep track of your activity as a sender (they identify you in a variety of ways, including your IP address and domain) and monitor the number of bounces that you produce (email delivery errors). If that amount exceeds certain parameters, action will be taken, varying from blocking your messages for a certain amount of time to reporting you to one or more blacklists. This will lead to even more bounces and more delivery problems. So, mail delivery errors can negatively impact your short and long-term deliverability.

Bounce management
In Recipients > List > Unreachable it is possible to check the details of each error relating to each individual sending, with details of the error message.
You can filter the list by error type, address group, or recipient status.
There are commands to manage the filtered recipients in the list, you will have to select the contacts you want to involve, or select them all and press the 'Move/Copy' button
You can:
Copy/move recipients to an existing group, including the "Unsubscribed" group
Create a new group to copy/move recipients to
Click on "Move" to start the process.
Automatic bounce management
MailUp helps you manage bounces, automating the "clean up" process in the platform. This system performs automatic bounce management to minimize the chances of the negative effect on your reputation. Error messages are parsed automatically and recipients' behaviors are monitored (opens, clicks) to determine whether a recipient should be unsubscribed or not.
A carefully calibrated system, built with a sophisticated algorithm created by MaiulUp team, temporarily unsubscribes recipients who, in a given period of time, return a number of consecutive bounce for the same reason, without having had recent activities. This will help customers automatically follow best practices and avoid to continue sending to email addresses that cannot receive communications.
At the end of the temporary unsubscribe the recipient will be automatically re-entered as subscribed. If a further bounce for the same reason is returned, the recipient will be unsubscribed temporarily for a period of time slightly longer.
Subsequently, if the inbox of the recipient continues to be unreachable it will be classified as "permanently unsubscribed to further bounces."

Here is an example of how our algorithm works:
CreativitLab uses the MailUp platform to send a daily newsletter to 1MM contacts. By monitoring campaign results, there are 25,000 soft bounces generated by full inboxes.
With a traditional system the delivery rate would be at most 97.5% and in one month CreativitLab would send 750,000 emails to unreachable recipients.
Using the MailUp algorithm instead, after 2 bounces caused by full inboxes the recipient is suspended for 3 days. On the fourth day it is automatically re-entered, thus beginning to receive the daily newsletter again.
If after the temporary unsubscription two more consecutive bounce, caused by full inboxes, are recorded, the recipient is automatically unsubscribed for 6 days and then re-entered again. The automation is repeated up to 6 months. At the end of this process, if the recipient is still not reachable, he is permanently unsubscribed. On the other hand, if during this period, the recipient performs an activity on any received mail (a sign that the box has been cleaned up or reactivated) the contact is subscribed again and the counters are reset. In this way, during a month a contact will have received fewer emails (8 in total) saving 550,000 emails in a month with a delivery rate higher than 99%.
Hard bounce
When a Hard Bounce is received (e.g. 550 5.5.1 "Mailbox not found" or "Unknown user"), that recipient is not included in future mailings. This is true after the first HB and leads to better deliverability for the rest of the list. This task is performed automatically.
If a recipient that generated an HB is included in a campaign, the message is not sent and an HB is generated automatically, and added to the HB count for that account. The addresses will be unsubscribed permanently after the first hard bounce"
The reason why addresses are not immediately unsubscribed is that this allows the list administrator still find those recipients in the "Subscribed" group and in the list of recipients for a certain message. If the recipient were immediately unsubscribed, details on the error would not be visible.
Soft bounce and Mail block
The system automatically manages temporary delivery errors (Soft Bounces) that fall in the categories: SB, SBDF (Domain failure) and SBMF (Mailbox full) and other errors classified as Mail Block (MB*) temporally unsubscribing the recipient for a variable period of time, re-entering it later automatically. This process will be repeated several times until the recipient is definitively unsubscribed or the problem is solved.

You can check at any time which addresses have been automatically unsubscribed.
Go to Recipients > List > select "Unsubscribe Reason" from the conditions to be shown, choose the channel and then the reason "For repeated errors (temporary unsubscription)". Then, add a condition also "For repeated errors (permanent unsubscription)"