Set up sending · Updated Oct 8, 2026

Connect your mailboxes

In short

Senders holds the mailboxes your campaigns send from. They stay yours: SendPath sends through them and reads their replies.

How many mailboxes you need

Each mailbox should send about 30 campaign emails a day. More than that, and its mail starts landing in spam. So to send more, add mailboxes rather than raising one mailbox's limit. Every plan has unlimited mailboxes.

Under 100: Mailboxes: 1–4; Domains (2–3 mailboxes each): 1–2

100–1,000: Mailboxes: 4–35; Domains (2–3 mailboxes each): 2–12

1,000–10,000: Mailboxes: 35–350; Domains (2–3 mailboxes each): 12–120

Emails a day	Mailboxes	Domains (2–3 mailboxes each)
Under 100	1–4	1–2
100–1,000	4–35	2–12
1,000–10,000	35–350	12–120

Many senders use a second domain for cold email (for example acme-mail.com next to acme.com), so a problem never touches the domain your team uses every day.

Connect a mailbox

Step 1: On Senders, click Connect sender.
Step 2: Pick where your email lives (see the table below) and follow its steps.
Step 3: If the mailbox is new, tick Warm up this mailbox. Warm-up never starts unless you ask.
Step 4: Back on Senders, check the mailbox's health. Fix anything red before you send from it.

The Senders page: health cards, the Google Workspace connection and domain health, with Connect sender at the top right. — Senders. 1: Connect sender. The cards and Domain health show how your mailboxes are doing.

Google Workspace: One click. A Workspace admin can also connect the whole domain at once and pick which people's mailboxes to add.
Microsoft 365 / Outlook: One click: sign in with Microsoft and allow access.
Gmail, Yahoo Mail: The address and an app password, not your normal password. The connect screen links to where you create one.
Any other mailbox: The address and its password. SendPath fills in the server settings for sending (SMTP) and reading replies (IMAP); you can change any of them.
Sending services: Resend, Mailgun, Brevo, SendGrid, Amazon SES and Mailjet connect with an API key (Connect with API). Your domain must be verified at the service first.

A mailbox connected through a sending service doesn't warm up, and SendPath reads its replies only if you also give the mailbox's own password. Bounces are read from the service.

Connect a mailbox: one-click cards for Google Workspace and Microsoft 365, then sending services with an API key. — Connect a mailbox: pick where your email lives.

Mailbox health

Each mailbox has a health score out of 100 and one of three states:

Healthy: Sends normally.
Attention: Still sends, but something should be fixed: no DMARC record, DKIM not confirmed yet, or bounces over 2%.
Blocked: Sends nothing until it's fixed: the login was rejected, SPF fails, or bounces went over 5%.

Open a mailbox to see why. Why this sender isn't fully healthy lists each problem, and DNS checks shows the exact record to add. DNS is checked again every day on its own; Re-check checks it now.

Daily cap and sending window

Daily cap: The most emails the mailbox sends in a day: 50 unless you change it (1 to 2,000). Campaign emails go first, and warm-up uses what's left.
Sending window: Optional hours the mailbox may send in, in the workspace's timezone. Without one it sends whenever a campaign's schedule allows.

Change the cap under Limits and replies on the mailbox's page, then Save.

Where replies go

SendPath reads replies from the mailbox that sent the email. If the mailbox has a Reply-to address, replies go there instead, and SendPath never sees them: they don't show in Replies, and unsubscribe requests in them aren't caught. Leave Reply-to empty.

When a mailbox is stopped for bounces

A mailbox stops when more than 5% of its emails bounce (counted once it has sent 50). The addresses that bounced are already suppressed.

Step 1: Re-verify the rest of the list on Verification, so the next emails don't bounce too.
Step 2: Open the mailbox and click Resume sending. Its bounce count starts again from zero.

If it goes over 5% again, it stops again, to protect your domain.

If something's wrong

Gmail or Yahoo says the password is wrong.: Use an app password, not your normal one. Gmail only offers app passwords once 2-Step Verification is on.
A mailbox says the credentials were rejected.: Its password changed or its access was removed. Open the mailbox and use Replace password, or connect it again.
A mailbox is Blocked for SPF.: Add or fix your SPF record. See SPF.
Replies from one mailbox never show up.: Clear its Reply-to, and check that Reply sync on its page works.

Was this page helpful?

Set up your domain (DNS)The four DNS records that prove your mail is yours, what to add for each, and where to add them.Warm-upHow warm-up builds a new mailbox's reputation, how long it takes, and how to read the Warm-up page.Deliverability checklistEverything to check before and while you send, in one list.

Something missing or wrong? Email support@sendpath.ai.