As part of your efforts to maintain a healthy inbox delivery rate, you should be monitoring your email bounce rates. If your hard bounce rate climbs above 5%, you should take a closer look at what’s going on. If your hard bounce rate hits 10% or more, you should be concerned about your data quality.
If you have a high hard bounce rate, it is likely that you have a high number of invalid addresses. An invalid address is an address that has never existed or no longer exists, so mail will never be delivered to these addresses. Marketo automatically stops sending to these addresses, so you do not need to worry about suspending or removing them. But having a high invalid address rate could cause you major delivery problems and reputation issues, and could indicate problematic data sources or list segmentation practices that should be reevaluated.
A high invalid address rate can lead to outright blocking of your mail at major ISPs. Many ISPs monitor the number of invalid addresses being sent to at their domains by specific senders. Once a certain threshold is hit, those ISPs will block mail coming from the offending sender.
ISPs behave this way because they view a high rate of invalid addresses as an indication of problematic data practices of the sender. At best, a high invalid address rate means you are not sending to an engaged, active audience. At worst, it means that you are sending to purchased or rented lists, which is a violation of Marketo’s Email Use and Anti-Spam Policy. Chances are, if you have a high invalid address rate, there are other issues with your data that could also contribute to.
If you receive a notification that we have noticed a high invalid address rate associated with your mailings, you should ask yourself some questions about your list management practices. Below are some things to consider:
- Have you recently added any new leads or lead sources? Purchased lists are often full of invalid addresses. We often find that purchased lists contain numerous addresses from domains that don’t even exist any more. While you can use purchased lists to bulk up the data you have for existing leads, you cannot use them to bulk up your lead database.
-Have you recently targeted old or inactive leads? We strongly recommend that you never send to an address that you haven’t mailed to for over a one year. You should be mailing to your contacts at least every six months. This will help prevent high invalid address rates, and will also help keep you and your content fresh in your contacts’ minds. If you do have to send to older leads, you should break up your lists and send to your most recent and active contacts first.
- Who are you targeting? Some senders have more problems with high invalid address rates because of their target audiences. For example, targeting .edu domains often causes high invalid address rates because these are school addresses that have a higher turnover rate. B2B campaigns may sometimes have higher invalid address rates because of similar turnover rates at businesses.
The best way to avoid high invalid address rates is to send to opted-in, engaged recipients. To help with this, a lot of senders clear out their inactive leads every six months or so. An inactive lead is a contact that has taken no action in the given time period— they haven't opened an email, clicked a link, visited your webpage, attended a webinar, and so forth. This can help with both your high invalid address rates and spam complaints. Inactive leads are a dangerous group to continue mailing to because their behavior proves that they do not want to interact with your mail, and will therefore likely complain to us or to their ISPs about it.