Send email

Mailgun

Email delivery service with a REST API and SMTP that sends, receives and tracks transactional and bulk email.

Rate limits

Metrics API: 500 requests per 10 seconds18
Rate limit headers: X-RateLimit-Limit, X-RateLimit-Remaining, X-RateLimit-Reset; HTTP 429 when exceeded10
Send API rate limit: Not published10

Other limits

Recipients per batch call: 1,00013
Send options size: 16 KB total for parameters starting with o:, h:, v: or t:11
Scheduling window: 3 or 7 days depending on plan11
Delivery window (o:deliver-within): 5 minutes to 24 hours11
Suppression import file: 25 MB per CSV12
Mailing list members per bulk add: 1,00012
Route filter or action length: 4k characters16

Read from Sinch’s own pages on 2026-11-04. Every number links to the page a value came from. For agents, the same facts as markdown: /tools/send-email/mailgun.md