Sender reputation is the level of trust that mailbox providers assign to your sending domain and IP address, and it is the single biggest factor in whether your email reaches the inbox or the spam folder.
In depth
Providers score reputation continuously from signals including spam-complaint rate, spam-trap hits, bounce rate, authentication results and — increasingly — positive engagement such as opens, replies and messages moved out of spam. Reputation attaches to both the domain and the IP, so it follows you even if you change one. It is slow to build and fast to lose: a single mailing to a bad list can undo months of good sending.
Example
Two companies sending identical content can see very different inbox placement purely because one has a complaint rate of 0.02% and the other 0.4%.
Related terms
See our full email marketing glossary or the complete email marketing guide.