> ## Documentation Index > Fetch the complete documentation index at: https://help.lobyco.com/llms.txt > Use this file to discover all available pages before exploring further. # Deliverability > What decides whether your emails reach the inbox, and how to warm up a new sending domain. Deliverability is whether your emails reach customers' inboxes, rather than being blocked or sent to spam. An email can be delivered to the customer's mail server and still land in their spam folder. Mailbox providers such as Gmail and Outlook decide where it goes, based on five things. | Factor | What it is | | - | - | | [Authentication](#authentication) | Proving to mailbox providers that you're allowed to send from your domain. | | [Sending reputation](#sending-reputation) | Your track record as a sender, built up over time. | | [Content quality](#content-quality) | How relevant and trustworthy your emails look. | | [Bounces](#bounces) | Addresses that can't receive email, and how they affect your reputation. | | [Unsubscribes and engagement](#unsubscribes-and-engagement) | Sending only to customers who agreed, making it easy to unsubscribe, and sending less to customers who don't engage. | ## Authentication Authentication is set up for your sending domain outside Lobyco Nexus. The portal has no settings for it. ## Sending reputation Your reputation is like a credit score with mailbox providers. A poor one sends your emails to spam, or gets them blocked. | Signal | Effect on your reputation | | - | - | | Many spam complaints | Hurts it | | Many bounces | Hurts it | | Sending to customers who never open your emails | Hurts it | | A sudden jump in how many emails you send | Hurts it | | Good open and click rates | Helps it | | Sending at a steady pace | Helps it | ## Content quality Mailbox providers read your email to judge whether it's spam. Write for the customer. Say what's in it for them, keep the sales language calm, and personalise where you can. * Mix text and images. An email that's only images looks suspicious. * Give it one clear button or link to act on. * Check that it reads well on a phone. Use the preview in the [email editor](/business-documentation/communication/email#design-the-email-in-activity-content). These make an email look like spam, so avoid them: * a subject line in capitals * lots of exclamation marks * link shorteners, such as bit.ly * a lot of links to other sites ## Bounces A bounce is an email that couldn't be delivered. There are two kinds. * A hard bounce is permanent. The address doesn't exist, or its domain doesn't. Each new email to it hurts your reputation. * A soft bounce is temporary. The mailbox might be full, or the server might be down for a while. A later email can still get through. An address that keeps bouncing hurts your reputation too. Lobyco records bounces, but sending doesn't skip those addresses. A segment can't pick customers by bounces either, so you can't leave them out of an audience. ## Unsubscribes and engagement * Send only to customers who agreed to get email. Sending doesn't check consent for you, so build every email audience from a segment that checks email consent. Never use a bought or copied list. * Add the [Unsubscribe Link](/business-documentation/communication/email#design-the-email-in-activity-content) to every email, and never hide it. * Send less often to customers who don't engage. A segment can't pick customers by the emails they opened, so pick customers who haven't shopped or used your app for a while. Try a campaign to win them back first. If they still haven't shopped or used your app after 90 to 180 days, stop sending to them. ## Warm up a new sending domain A new sending domain has no reputation yet. Neither has one that hasn't sent email for a while. If you send a lot of emails from it straight away, mailbox providers treat that as a warning sign. So start small and send a little more each day. * Start with your most engaged customers, such as those who shopped or used your app recently. * Increase the number gradually, over two to four weeks, until you reach your full list. * Send every day. Gaps slow down how fast your reputation builds. * Avoid sudden jumps in volume, even halfway through. * Leave out customers who don't engage until the warm-up is over. A common plan is 14 days, sending 20 to 30% more each day than the day before. This example starts at 500 emails a day and grows by about 30%. You can start lower or higher, depending on your list and how much you've sent before. What matters is a steady daily increase. | Day | Emails | Day | Emails | | - | - | - | - | | 1 | 500 | 8 | 3,150 | | 2 | 650 | 9 | 4,100 | | 3 | 845 | 10 | 5,330 | | 4 | 1,100 | 11 | 7,000 | | 5 | 1,430 | 12 | 9,100 | | 6 | 1,859 | 13 | 11,830 | | 7 | 2,420 | 14 | 15,200 | To send to a different group of customers each day, see [Warm up email sending](/business-documentation/use-cases/warm-up-email-sending-in-daily-batches). ### If the warm-up is interrupted | Gap | What to do | | - | - | | 1 to 2 days | Carry on with the next day's number. | | 3 to 7 days | Go back to the last number that went well, then increase by 20 to 30% a day again. | | About 2 weeks | Restart at about half the last number, then increase by 20 to 30% a day. | | A month or more | Start the warm-up again from a low number. | ## Where deliverability is managed In Nexus, you control who gets each email, how many go out each day, what the email says and who it's from. You set these when you [create an email](/business-documentation/communication/email). Who gets it comes from the audience or the segment before it. Your sender address has to be on a domain Lobyco has set up for your programme, or the email won't publish. If that happens, see [Troubleshooting](/business-documentation/communication/email#troubleshooting) on Emails. ## Next steps * [Emails](/business-documentation/communication/email) walks you through the email form, from the subject line to publishing. * [Warm up email sending](/business-documentation/use-cases/warm-up-email-sending-in-daily-batches) shows how to split a large list into one group per day. * [Recipients](/business-documentation/communication/triggering) explains when each kind of email is sent. * [Lifecycle](/business-documentation/communication/lifecycle) covers what you can change once an email is published. This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.