Compare
Azure tenant vs Microsoft 365 packs
Both are Microsoft mailboxes. The difference is not quality, it is how much of your fleet one bad week can take with it.
| Azure tenant | M365 packs | |
|---|---|---|
| Mailboxes | 100 per tenant | 3 per domain |
| Per inbox cost | Far lower | Higher |
| Whose reputation is at stake | Shared across the tenant — 25, 49 or 100, your choice | Separate on each domain |
| Loss when something burns | Potentially the tenant | Three inboxes |
| Suits | 1,000+ sends a day, disciplined lists | Under 1,000 a day, mixed clients |
The honest rule of thumb
Below about 1,000 sends a day, buy packs. The isolation is worth more than the saving, and a burned domain costs you three inboxes rather than a hundred.
Above it, tenants become compelling, but only with verified lists, cohort ramping and daily bounce monitoring for the first fortnight. Teams who run tenants like cheap packs lose them.
Agencies often want both
Packs per client for isolation, a tenant for bulk top-of-funnel where the list quality is controlled. Mixing is normal and usually correct.