How to isolate and retire toxic mailboxes?

When individual mailboxes become toxic, isolating and retiring them protects other sending infrastructure.

Identification:

• Track metrics per mailbox, not just per campaign
• Watch for mailboxes with higher bounce or complaint rates
• Check individual mailbox reputation where possible
• Note mailboxes triggering rate limits

Isolation steps:

• Remove problematic mailbox from active campaigns
• Stop warmup activity for that mailbox
• Don't shift its volume to other accounts (spreads problems)
• Document the issue and timeline

Investigation:

• What campaigns ran through this mailbox?
• What lists were contacted?
• Any authentication or technical issues?
• Pattern of complaints or blocks?

Retirement process:

• Plan replacement mailbox before full retirement
• Allow new mailbox to warm before needing it
• Transfer any legitimate contacts if appropriate
• Keep retired mailbox active to receive replies
• Don't delete until reply handling is complete

Prevention:

• Rotate mailboxes to avoid overuse
• Monitor individual account health
• Set lower limits on newer accounts
• Have replacement accounts warming in reserve