Regions & deliverability

Sending regions, DKIM signing, return paths and what delivery events mean.

Sending regions

Bytesms operates its own sending servers (MTAs) in several regions. Each domain is attached to one region when you add it, and all mail from that domain leaves from that region.

region	Location	Return-path target
`ap-southeast-7`	Thailand (default)	`mta.bytesms.com`
`ap-southeast-1`	Singapore (coming soon)	`mta-ap-southeast-1.bytesms.com`
`eu-central-1`	Frankfurt, Germany	`mta-eu-central-1.bytesms.com`

Singapore (ap-southeast-1) is not open to new domains yet while its sending IP builds reputation. A domain created with region: "ap-southeast-1" is currently placed in the default region (ap-southeast-7) instead.

Pick the region closest to your recipients or required by your data-residency rules with the region field of create domain. Always publish the DNS values the API returns — the return-path target differs per region.

How your mail is authenticated

DKIM — signed twice

Every message is DKIM-signed with your domain's key (d=your domain, selector bytesms), which is what DMARC alignment needs. In addition, like Amazon SES, messages carry a second signature for bytesms.com, so mailbox providers can attribute the mail to the platform as well. You only publish your own DKIM record.

SPF via the return path

The envelope sender (bounce address) is on your return-path subdomain, e.g. bounces+…@send.example.com. Its CNAME points at the region's bounce host, which publishes the SPF record for our servers — so SPF passes and aligns with your domain (relaxed alignment) without editing your root SPF record, and bounces come back to Bytesms.

DMARC

Publish a DMARC record at _dmarc.<domain>. Start with p=none and a rua address to collect reports, then move to quarantine or reject. Large mailbox providers require DMARC for bulk senders.

What delivery events mean

Event	Meaning
`email.sent`	Our server accepted the message and queued it for delivery.
`email.delivered`	The recipient's mail server (MX) accepted the message with a 2xx reply. It does not tell you whether it landed in the inbox, the spam folder, or was filtered later.
`email.delivery_delayed`	A temporary failure (4xx or deferral). Our server keeps retrying.
`email.bounced`	A permanent failure — either rejected during delivery or reported later by an asynchronous bounce (DSN), which can arrive after email.delivered.
`email.complained`	The recipient marked the message as spam (where the provider reports it).

Suppression list

Addresses that hard-bounce or complain are added to your suppression list and skipped on future sends. You can review and remove entries in Dashboard → Emails → Suppressions.

Deliverability checklist

Verify DKIM and the return path, and publish DMARC.
Send transactional and marketing mail from different subdomains (e.g. mail. and news.).
Include a plain-text part (Bytesms generates one from your HTML if you don't) and avoid link shorteners and image-only emails. The dashboard shows content warnings when composing templates and broadcasts.
Broadcasts always get an unsubscribe link and one-click List-Unsubscribe; for transactional mail you can set your own List-Unsubscribe header.
Remove bounced addresses and keep complaint rates well below 0.3%.
Ramp up volume gradually on a new domain.

Workspaces with sustained high bounce or complaint rates are paused automatically (403 sending_paused) to protect every customer's reputation; contact support to resume.