How to Warm Up Fastmail: Settings, DNS, and Ramp

To warm up Fastmail, connect with a Fastmail app password, use IMAP imap.fastmail.com:993 SSL and SMTP smtp.fastmail.com:465 SSL, then ramp from 3 warm-up emails per day. If you skip DNS or volume control, early outreach is more likely to hit spam or fail authentication. This guide gives the setup, ramp, checks, and fixes.

BobWork connects Fastmail through Other IMAP + SMTP, because Fastmail is a standards-based mailbox provider. You can use the free warm-up tool to start at low volume, rescue BobWork-generated warm-up mail from spam, and measure spam placement from real receiving inboxes. For timing, caps, and readiness rules, see the warm-up strategy.

What settings does Fastmail need?

Fastmail needs an app password for third-party mail clients. Do not paste your normal Fastmail account password into a warm-up tool or external mail client.

Use Fastmail’s current help pages before changing production mailboxes: Fastmail server names and ports and Fastmail app passwords. The settings below match the official values verified for Fastmail.

A clean connection is only the first step. The sending domain also needs SPF, DKIM, and DMARC. Then the mailbox needs gradual, consistent activity before you use it for outreach.

For background on authentication, read SPF, DKIM and DMARC for cold email. To check records directly, use the SPF checker, DKIM checker, and DMARC checker.

How do you connect Fastmail?

Create a Fastmail app password first. Name it clearly, such as BobWork warm-up, so you can revoke it later without breaking other mail clients.

Copy the app password once and store it safely. If you lose it, create a new app password instead of trying to recover the old one.

In BobWork, sign in with your email code. BobWork accounts do not use passwords. Add a mailbox, choose Other IMAP + SMTP, and enter the Fastmail settings from the table above.

After saving, BobWork tests both sides of the connection. IMAP must log in and read the mailbox. SMTP must log in and send from the mailbox. If either side fails, fix the connection before starting warm-up.

BobWork uses a shared warm-up network by default. Every active mailbox on the service exchanges warm-up emails with other active mailboxes across accounts. One Fastmail mailbox is enough to start.

If you prefer, switch to a private pool in Mailbox pool → Pool mode. In private mode, only your own mailboxes write to each other, and you need at least two mailboxes.

Warm-up content is generated by the engine: short plain-text office notes, no links, no images, and first-name greetings. Users do not write pool messages. Only mail carrying the engine’s hidden header is touched. Real mail is never read, moved, or answered.

Which DNS records must pass?

Do DNS before volume. A warmed mailbox on an unauthenticated domain is still weak.

Fastmail DNS values can vary by domain setup and account configuration. Use Fastmail’s current admin screens or DNS help for the exact SPF include value, DKIM selector records, and verification records. Do not copy DNS values from an old blog post.

SPF is a TXT record on the sending domain. It lists which services may send mail for that domain. If you already have SPF, merge Fastmail’s include into the existing SPF record. Do not publish two SPF TXT records for the same domain.

DKIM is published as selector records in DNS. Add the selector names and TXT values exactly as Fastmail gives them. Then verify that the public key is visible.

DMARC is a TXT record at _dmarc.yourdomain.com. For an early domain, start with p=none so you can observe authentication before moving to a stricter policy.

BobWork checks SPF, DKIM, and DMARC daily and shows results per domain. The domain checker looks for common DKIM selectors, but Fastmail’s own setup page should remain the source for provider-specific values.

If the domain is new, do not connect DNS in the morning and start cold outreach in the afternoon. Let DNS propagate, send normal internal mail, then begin the warm-up ramp.

How do you warm up Fastmail?

Use a gradual ramp. BobWork starts at 3 emails per day, adds 2 per day, and caps at 30 per day by default. Weekends run at 30%. Sends are spread between 09:00 and 18:00 in the mailbox’s own time zone, with randomness.

A pair of mailboxes never writes to each other twice within 3 hours. Peers on a different domain or provider are picked twice as often. About 40% of received warm-up mail gets a reply, and threads end after 3 messages.

Here is the standard ramp path. Weekend days may send less because weekend warm-up runs at 30%.

The next step reaches the default 30/day cap. You can edit the cap per mailbox up to 100, but do not use the maximum just because it exists.

Our published baseline is 7 days for an existing domain and 2–3 weeks for a new one. For cold outreach, keep real sends around 30–50 per mailbox per day and add mailboxes rather than forcing one mailbox to carry all volume.

During active campaigns, keep warm-up running at 10–15 per day. That keeps normal mailbox activity present while real replies, bounces, and unsubscribes begin to shape the sender profile.

If you are planning a longer ramp, use the email warm-up schedule generator. If the domain is new, read email warm-up for a new domain before sending campaigns.

How do you fix Fastmail errors?

Most Fastmail warm-up problems are connection problems, DNS problems, or volume problems. Fix them in that order.

If BobWork warm-up mail lands in spam, the rescue flow moves its own warm-up mail to Inbox, marks it read, labels it Warm-up, and archives it after 24 hours. This applies only to BobWork-generated warm-up mail identified by the engine.

If a mailbox’s spam rate goes above 5%, pause that mailbox for a few days. Do not compensate by raising volume on another weak mailbox. Fix DNS, connection health, list quality, and message content first.

If Gmail recipients are a large part of your audience, use Google Postmaster Tools once you have enough traffic for dashboards to populate. Google’s sender guidance says to keep spam complaint rates under 0.1% and avoid reaching 0.3%. See Google’s Email sender guidelines.

If you send to Yahoo addresses, follow Yahoo’s sender requirements too. Yahoo requires SPF and DKIM, DMARC with alignment, and low spam complaints for bulk senders. See Yahoo sender best practices.

When is Fastmail ready?

A Fastmail mailbox is not ready just because SMTP works. It needs enough warm-up history and low spam placement.

In BobWork, a mailbox is ready for outbound when it has warmed for at least 7 days, has a 7-day spam rate of 3% or lower, and has received at least 30 warm-up emails.

The health score runs from 0 to 100. Healthy is 85 or higher. Watch is 60–84. At risk is below 60. Blocked means login or permission failed.

Start small after the mailbox is ready. Send only to clean, relevant contacts. Use plain copy, one clear ask, and an unsubscribe route when appropriate. A reply should stop the sequence for that contact.

If you use BobWork Outbound later, only mailboxes that pass the ready gate can send. The first week after ready is capped at 30 cold emails per day per mailbox, then 50 per day after that. Warm-up keeps running on the same mailboxes while they send.

For more detail on safe outreach volume, read How Many Cold Emails Per Day Is Safe Per Mailbox?. If you are warming several Fastmail and non-Fastmail inboxes together, use the multiple-mailbox guide to avoid pushing one domain too hard.

Do this now

Use this checklist before you send cold email from Fastmail.

Manual warm-up is possible, but it is hard to maintain replies, spacing, spam rescue, and cross-provider variety every day. If you want the comparison, read Manual Email Warm-Up vs Automation.

Set up Fastmail with an app password, verify DNS, and let the ramp run before you ask the mailbox to sell. BobWork Email Warm-up is free for up to 10 mailboxes, with no credit card and no time limit, so you can warm the account first and decide on outbound later.

Fastmail warm-up FAQ

Can I use my normal Fastmail password?

No. Fastmail requires an app password for third-party mail clients. Use the app password when connecting over IMAP and SMTP, not your regular Fastmail account password.

What are the Fastmail IMAP settings?

Use imap.fastmail.com on port 993 with SSL. In BobWork, connect it with the Other IMAP + SMTP preset and use your full Fastmail email address as the username.

What are the Fastmail SMTP settings?

Use smtp.fastmail.com on port 465 with SSL. Use your full Fastmail email address as the username and a Fastmail app password as the password.

How long should I warm up Fastmail?

Use at least 7 days for an existing domain. Use 2–3 weeks for a new domain. Start at low volume, watch spam placement, and do not send outreach until the mailbox passes readiness checks.

Do I need SPF, DKIM, and DMARC?

Yes. Add SPF, DKIM, and DMARC for the sending domain. Get the exact SPF include value and DKIM selectors from Fastmail’s current DNS setup page, then verify the records.

Can BobWork warm up Fastmail?

Yes. Fastmail connects through Other IMAP + SMTP. BobWork supports any IMAP+SMTP mailbox when it can send through SMTP and receive through IMAP.

When is Fastmail ready for outbound?

In BobWork, it is ready after 7+ days warming, a 7-day spam rate of 3% or lower, and at least 30 warm-up emails received. Start outreach slowly after that.

Frequently asked questions