Mailboxes

A mailbox is a real sending account — the email address, authentication credentials, signature, optional BCC address, and daily pacing configuration used to dispatch campaign emails and detect replies.

Mailboxes are independent of brands and are unlimited on every Aimly plan. Any mailbox can be paired with any brand when creating a campaign.

Deliverability best practice

Send cold outreach from a dedicated secondary domain (for example, alex@mail.example.com) rather than your primary corporate domain (alex@example.com) to isolate your core business email reputation.

Adding a mailbox

Mailbox Connection & Rate Limiting

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Open Mailboxes under Configurations in the Aimly Email sidebar and click Add Mailbox. Setup follows a four-step wizard:

Step 1: Signature & extras

Configure optional sender metadata applied to outgoing mail from this mailbox:

• Email Signature (optional, up to 1,000 characters) — appended automatically to outgoing emails sent through this mailbox. If the campaign's brand includes a logo, the logo renders inline immediately below the signature.
• BCC Address (optional, up to 254 characters) — blind-copied on every outgoing email sent from this mailbox (for example, a CRM logging address or compliance archive).

Step 2: Rate limiting

Choose how Aimly paces outgoing mail from this mailbox:

Mode	Behavior
Automatic (Adaptive) (recommended)	Starts immediately at a safe baseline of 20–23 emails/day and scales automatically based on consistent sending history through Aimly (baseline up to 2,000, about 2,300 emails/day at the top of the pacing range).
Fixed Daily Limit	Paces sends at about your number to 1.15× that number per day (1 up to the mailbox's current adaptive baseline). Never auto-increases.
Skip rate limiting	Disables inter-email pacing delays so queued messages dispatch immediately. Use only when you intentionally accept the sender-reputation risk of unthrottled bursts.

Step 3: Connect your mailbox

Select an Email Provider (Gmail, Outlook, Yahoo, or Custom):

• Gmail (Sign in with Google) — opens a Google OAuth popup and connects via the Gmail API. No email address, host, or password fields are shown; your Google account supplies the address automatically. Once authorized, click Finish Creating Mailbox (Step 4 is skipped).
• Outlook (Sign in with Microsoft) — opens a Microsoft OAuth popup and connects via Microsoft Graph. Once authorized, click Finish Creating Mailbox (Step 4 is skipped).
• Yahoo — enter your Email Address (up to 254 characters). Aimly pre-fills smtp.mail.yahoo.com:587, imap.mail.yahoo.com:993, and Sent folder Sent, then advances to Step 4.
• Custom (SMTP/IMAP) — enter Email Address, SMTP Host (max 255), SMTP Port (587 recommended), IMAP Host (max 255), IMAP Port (993 default), and Sent Folder (max 100, required). Use Custom for iCloud, Zoho, Fastmail, private mail servers, or when connecting Gmail/Outlook via an app password instead of OAuth.

If your browser blocks the OAuth popup for Gmail or Outlook, click the Open the sign-in page fallback link displayed in the modal. For provider-specific instructions, see Email provider integrations.

Step 4: Secure your mailbox (Yahoo and Custom only)

Enter the mailbox's App Password or Password (up to 200 characters). Aimly tests both the live SMTP and IMAP connections before saving the mailbox and reports the exact server error if either handshake fails.

How adaptive rate limiting works

When Automatic (Adaptive) is enabled, Aimly adjusts the mailbox's daily sending baseline once per day using actual sends recorded in Aimly:

• Initial pace — new mailboxes start with a baseline of 20 (allowing 20–23 emails/day, with randomized spacing across the day).
• Healthy growth (+15%/day) — sending within the daily target band (baseline to baseline × 1.15) increases the baseline by 15% for the next day, up to a ceiling of 2,000/day.
• Buffer zone — sending slightly below the baseline (within 5% or 2 emails) leaves the baseline unchanged.
• Idle or burst decay — days with zero or very low volume decay the baseline by ÷ 1.15 (floored at 20). Unthrottled bursts well above the safe ceiling also step the baseline back proportionally to protect mailbox health.

Editing, monitoring, and deleting mailboxes

• Editable vs. locked settings — after creation, you can update Rate Limiting, Signature & BCC, and Password (or click Reconnect under Access for Google/Microsoft OAuth accounts). The email address, SMTP/IMAP hosts, ports, and Sent folder are permanently locked; create a new mailbox to use a different address or server.
• Immutable campaign binding — a campaign's assigned mailbox cannot be changed after the campaign is created.
• Consecutive failure alerts — if a mailbox fails to deliver 3 consecutive emails, Aimly sends an alert email naming the mailbox to your account address (at most once every 6 hours per mailbox).

Deleting a mailbox deletes its campaigns

Deleting a mailbox permanently deletes every campaign configured to send from it, including those campaigns' templates, email history, and automation sequences, and frees the email address for reuse. Aimly lists all affected campaigns and requires typing the exact mailbox email address before confirming.