🔀 SMTP Rotation: Spread Sends Across Many Connections

Rotation shares your sending between all your connections instead of pushing everything through one. That spreads the reputation load: 1,000 emails over 5 connections is about 200 each. You can rotate across any providers, including several accounts with the same provider.

Failover always stays underneath. Whichever connection rotation picks first, a connection that reports an error is skipped and the next one delivers the email.

Where to find it:

Open Delivery, then Sending, and scroll below the providers table to the Send Rotation & Warmup card. It appears once you have at least one active connection that is not WordPress wp_mail. Until then it shows a short note asking you to add one.

The card shows how many emails were sent today across how many connections, then the routing modes, the Strict DKIM guard, "Who the email says it is from", and a table of your connections.

The three modes:

• Priority + failover: the starting mode, and the way the Mailer has always worked. The lowest priority number sends everything, and the next takes over if it has trouble or reaches its cap.
• Rotate evenly: every send goes to the eligible connection that has sent the least today. The split stays even all day, and a connection you add in the afternoon catches up instead of being flooded.
• Weighted shares: you give each connection a Weight, for example 60, 20 and 20, and sends follow those proportions. The Mailer picks the connection whose sent today is lowest compared to its weight. A Weight of 0 keeps a connection out of the rotation but still available as backup.

Switching rotation on, step by step:

1. Open Delivery, then Sending, and scroll to Send Rotation & Warmup.
2. Choose Rotate evenly or Weighted shares.
3. For Weighted shares, type a number from 0 to 1000 in each connection's Weight box. Only the proportions matter, so 60/20/20 and 3/1/1 behave the same. A new connection starts at 1.
4. Choose who the email says it is from (below).
5. Click Save rotation & warmup. A small Saved label confirms it.

The connections table:

• Connection: the name, then its provider, priority and From email.
• Sent today: emails sent today, and the Daily limit underneath when one is set.
• Share: this connection's part of today's sends, as a percentage.
• Capacity left: how many more it may send today, after its Daily limit and any warmup cap. It says unlimited when neither is set.
• Weight: used only in Weighted shares mode.
• Warmup: the Warm up tick box and its pace. See Warmup: Drip A Big Send Through A Cold Server.
• Authentication: a badge for the sending domain. See The DKIM Guard: Rotate Only Through Authenticated Senders.

Only active connections are listed, and WordPress wp_mail is never part of rotation.

Who the email says it is from:

Rotation changes which server carries an email. This setting decides whether the sender address travels with it.

• The email's own From, always: the starting choice. Every connection sends with the From of the email. Right for everyone sending from one domain that all their services are authorised for.
• Each connection's own From: when a connection has its own From email, the email goes out as that address and From name. Replies still go to the email's Reply-To. If the email had no Reply-To, its original From becomes the Reply-To, so replies always reach you. Use this for warmup subdomains, where each server may only send as itself.
• Keep the From, change only the hidden sender: readers still see the email's From. Only the behind the scenes sender that your mail server checks is switched to the connection's address. This applies to Bring-your-own SMTP connections; the API services handle it themselves. Try a test send before a broadcast.

A connection with no From email of its own is left as it is under the second and third choices.

While rotation is on with The email's own From, always, the checks before you send a broadcast include one called "Sender matches the server". It lists any connection in the rotation whose own From uses a different domain, so you can switch the setting before anything is refused.

What stays the same:

• Daily limits and warmup caps still apply. A connection that is full for the day drops out of the rotation until tomorrow.
• When every connection is full, the rest of the queue waits and continues when capacity returns. Nothing fails, and nothing falls back to wp_mail.
• A broadcast's Send via box still wins for that broadcast: the chosen connection goes first and the rest stay behind it as backup.
• If no connection is eligible for rotation (for example every weight is 0), the Mailer simply sends in priority order.

A real example:

Leafwise Gardening rotates three connections with Weighted shares: Amazon SES (main) weight 60, SMTP2GO weight 20, Postmark (broadcast stream) weight 20. All three send as anna@yoursite.com, so "Who the email says it is from" stays on The email's own From, always. Today the table shows SES 412 sent (59 percent), SMTP2GO 188 (27 percent) and Postmark 96 (14 percent). SMTP2GO is warming up with a cap of 800, so once it reaches that cap the other two carry its share for the rest of the day.

Tips:

• Authenticate your domain at every provider in the rotation. Each one sends as your domain. See Deliverability: SPF, DKIM And DMARC.
• Give a brand new connection a small weight at first, or switch on its warmup.
• Use Weight 0 for a connection you want only as a backup.
• Set a Daily limit on every connection, so the shares never push one past its plan.
• Click Test on each connection after any change to its keys.

If something does not look right:

• If the shares do not match your weights early in the day, give it time. The picker always sends to the connection furthest below its share, so the split evens out as the day goes on. A connection that reaches its cap also drops out until tomorrow.
• If a connection never receives any rotated sends, check that it is Active, has Capacity left, has a Weight above 0 in Weighted shares, and is green when Strict DKIM guard is ticked.
• If emails through one server are refused with a message about the sender not being valid, switch "Who the email says it is from" to Each connection's own From, and give that connection its own From email.