Several times recently I've been asked if it’s OK to try to resend to email addresses flagged as undeliverable on a suppression list. The short answer is no.
To understand why, it’s necessary to understand how addresses get on the suppression list. While this can differ slightly from ESP to ESP, in general addresses are added for three reasons:
- Abuse complaint
Opt-outs and abuse complaints are pretty straightforward. A recipient clicks on the “unsubscribe” link or marks an email as spam, and the system adds them to the suppression list.
Undeliverables are a bit different. Hard bounces, which occur when emails get sent to bad mailboxes and bad domains, get added as soon as the system receives them.
Soft bounces generally get added after "X" number of consecutive bounces over a minimum "Y" number of days. The frequency varies but is long enough to prevent addresses from being added simply because they were blocked for a couple days.
So why would you not want to periodically retry these addresses to see if any had become valid? For starters, the vast majority of undeliverables are added correctly, and resending to them will simply result in hard or soft bouncing again, hurting your deliverability with most ISPs.
Secondly, when undeliverable addresses do become valid again, it’s usually for one of two reasons – neither of them good for you:
1) The ISP has reissued the addresses to new recipients. So while the email addresses may be legitimate, the people on the receiving end haven’t opted in to receive your mailings. As a result, these recipients are likely to flag your mail as spam, causing your abuse rate to spike.
2) The ISP or blacklist has reactivated the addresses as spam traps. Sending to these could get you blocked or blacklisted in a hurry. (Read more about spam traps.)
Occasionally, valid addresses get added to the master suppression list as undeliverable. But this is usually due to receiving erroneous bounce messages from the receiving server and is exceedingly rare, so it doesn’t justify a mass resend given the repercussions.
The bottom line? DON'T resend to addresses on your suppression list, as doing so could have a severe negative impact on your reputation and potentially get your IP address blacklisted.
More Deliverability Blogs:
1) “Feedback Loops: What They Are and What They Tell You About Your Email Program”
2) “10 Steps to Keep Bad Email Addresses Out of Your Database”
3) “Gmail’s New Unsubscribe Link and What It Means for Marketers”