If your distribution list send halts partway through, Microsoft has throttled your mailbox. ContactMonkey's alert system automatically notifies you and your Customer Success Manager when this happens. This article explains the three most common causes and how to fix each one.
Outlook Attachments in Email Body
Attaching files directly in Outlook limits your maximum file size to 4MB when sending with ContactMonkey. When you attach files to the email body in Outlook rather than embedding them through ContactMonkey, it can cause sending failures.
Solution: Embed your attachments through the File Manager instead of attaching them directly in Outlook.
Microsoft Outlook Sending Limits
Microsoft imposes sending limits on each email address. When you send to large distribution lists using Individual tracking, Outlook may throttle or stop your send entirely.
Solution: If you regularly send to large distribution lists, contact your Customer Success Manager about Email at Scale. This feature allows you to send to over 10,000 recipients at significantly faster speeds and is available for Office 365 and Gmail customers.
Heavy Outlook Signatures
Microsoft limits each mailbox to 150 MB of outgoing data per 5-minute window. A bloated signature can hit that ceiling in roughly 65 messages, at which point Microsoft cuts off the mailbox, ContactMonkey stops the send, and an alert goes out. The window is rolling, so a signature that's slightly heavier than last time can trigger throttling on a list that previously cleared without issue.
Solution: Skip Outlook's auto-signature when sending through ContactMonkey. Build your signature into the template footer instead.
What Happens When This Occurs
ContactMonkey's alert system automatically notifies both you and your Customer Success Manager when a distribution list send fails or stops midway. You'll receive an email alert showing whether your email was delivered successfully or encountered issues.