Target and Source Mailbox Size Differences
Understanding why mailbox sizes don't match after migration.
Last updated: 2025-01-15 Informational
Overview
The size of the target mailbox is often different from the size of the source mailbox after migration. This is due to environmental differences, not data loss. Different email systems store and process data differently.
Size Comparison
📥
Source
5.2 GB
≠
📤
Target
4.8 GB
=
✓
Normal
Expected
Primary Causes
Storage & Format Variations
- • Different compression methods between systems
- • Flat files versus database storage approaches
- • Varying content indexing strategies
Email Encoding Differences
- • Systems may use distinct formats (HTML versus plain text)
- • Different encoding protocols (UTF-8 or ASCII)
- • Communication protocol variations
Data Handling
- • Some emails may be ignored (non-mail items, duplicates)
- • These instances don't reflect migration failures
How to Verify Migration Success
Use Dashboard Statistics
The final size of the mailbox can't be used as an indicator of migration performance. Instead, review Dashboard statistics to verify migration success.
What to Check
- • Total items read vs. items migrated
- • Error counts and error types
- • Ignored items and reasons
- • Success rate percentage
Suspect Missing Content?
If you suspect content is missing, open a support ticket with the source email address,
message title, and timestamp for investigation.