Email warm-up is the process of building a new mailbox's sending reputation before it sends cold email. The mailbox sends a small, growing number of emails each day to other mailboxes that open them, reply and move them out of spam, so inbox providers see a history of wanted email.
How long it takes
Two weeks is a common minimum for a new mailbox, followed by about a week of gradually rising campaign volume. A typical pace starts at around 5 warm-up emails a day and adds a few each day.
Why it matters for cold email
A brand-new mailbox that suddenly sends hundreds of emails looks like a spammer and gets filtered. Warm-up gives it a reputation first. Keeping a small amount of warm-up running after campaigns start protects that reputation.
What it can't do
Warm-up doesn't fix a missing DNS record, a blocklisted server, a list full of dead addresses or an email people report. If warm-up emails themselves land in spam, check the domain's setup first.
Does an older mailbox need warm-up?
A mailbox that has sent normal email for months already has some history, so it needs less time. Starting cold email at a low volume and keeping warm-up running is still the safe way, because cold email is a new pattern for it.
Planning yours
The warm-up planner works out a day-by-day schedule. mailzy's built-in warm-up runs it for you, free and unlimited.