Microsoft 365 + MailKite

Microsoft 365 (Exchange Online) is the enterprise email standard. Use MailKite alongside M365 — MailKite for transactional email and inbound parsing, M365 for employee mailboxes.

What you need

• A verified domain with SPF + DKIM published
• Your API key (mk_live_…)
• Microsoft 365 tenant

Send email

Use MailKite SMTP for transactional email. Keep M365 for employee mailboxes.

# Use MailKite for transactional, M365 for employee mail
# Configure SMTP relay in M365 or use MailKite directly

# MailKite SMTP (simpler):
SMTP Host: smtp.mailkite.dev
SMTP Port: 587
SMTP Username: mailkite
SMTP Password: mk_live_...
From: noreply@yourdomain.com

# M365 SMTP AUTH (for reference):
# SMTP Host: smtp.office365.com
# Port: 587 (STARTTLS)
# Requires SMTP AUTH enabled per mailbox

Receive inbound email (optional)

Route specific addresses (support@, billing@) to MailKite for parsing. Keep employee mail in Exchange Online.

# MailKite inbound webhook for M365 routing
# Forward specific addresses to MailKite for parsing
# Keep employee mail in Exchange Online

# Configure DNS MX to point at MailKite
# for addresses you want to parse (e.g., support@, billing@)

Test it

Send via MailKite SMTP or API.

# Quick test
echo "Test" | swaks --to test@example.com --from noreply@yourdomain.com \
  --server smtp.mailkite.dev --port 587 \
  --auth USER=mailkite --auth-password mk_live_...

Troubleshooting

• M365 SMTP AUTH requires admin enablement per mailbox — a common friction point.
• MailKite has no such restriction — one API key, all addresses.
• Use DNS MX routing to split traffic: MailKite for support@, M365 for employee addresses.

See the SMTP relay docs for the full connection reference, or all integrations for other platforms.