Three controls in every mail client look interchangeable and aren't: moving a message to Junk, reporting it as spam, and adding the sender to your blocked senders list. Picking the wrong one is why the same newsletter keeps arriving after you've dealt with it four times.
The short version: dragging to Junk moves one message and teaches the filter nothing. Reporting as spam teaches it. Blocked senders skip the filter's judgement entirely. Three different mechanisms, three different results.
Here's what each one actually does, when to reach for it, and why the newsletter you keep blocking isn't the newsletter's fault.
Three Controls, Three Mechanisms
| Action | What it does | Affects future mail? |
|---|---|---|
| Drag to Junk | Moves one message between folders | No |
| Report spam | Moves it and feeds it to the classifier as a spam example | Yes, statistically — similar mail scores worse |
| Block sender | Adds the address to your blocked senders list | Yes, absolutely — that address always goes to Junk |
The first row is the one that surprises people. A folder move is a folder move. IMAP has no way to express "and I think this was spam", so a client that only moves the message has told the server nothing about why.
This is also why dragging junk out of your inbox in Outlook or Apple Mail never seems to improve anything. You've been tidying, not teaching.
How Reporting Spam Trains the Filter
Server-side filtering scores every incoming message against a large set of rules, plus a statistical classifier that learns from examples. The classifier is per mailbox, which is the important part: your idea of spam isn't your colleague's, and a recruiter's cold email is unwanted to one person and a job offer to another.
Report spam hands the message to that classifier as a labelled example. Not spam does the same in the other direction. After a handful of examples, similar mail starts landing where you want it.
Two honest caveats. Training is statistical, so it takes several examples before behaviour visibly changes — one report rarely does anything. And it works on similarity, so it's good at recognising a family of messages and poor at a single sender whose mail otherwise looks perfectly normal. For that second case you want blocked senders instead.
What Blocked Senders Actually Do
The blocked senders list is not a scoring input. It's an override: mail from an address on it goes to Junk regardless of how the message scores, what it says, or how legitimate it looks.
To add one, open any message from the sender, use More options in the toolbar and pick Block sender. The list lives under Settings → Blocked senders, where you can remove an entry with the × beside it.
The sender isn't notified, and nothing is bounced. From their side the message was delivered normally, which is exactly what you want — a bounce would confirm the address is live and tell them to try another one.
Because blocked senders bypass scoring, they're the right tool for the case training can't handle: a specific person or address you don't want to hear from, whose mail is otherwise indistinguishable from ordinary correspondence.
Where Blocked Senders Stop Working
They match one address, exactly. A spammer rotating through a1@example.com, a2@example.com and so on will outlast your patience. Each address needs blocking individually, and there are only so many entries.
There's a cap. Fifty addresses per mailbox. That's not a technical limit so much as a hint: if you're approaching it, the blocklist is the wrong tool for what you're doing.
Sender addresses are trivially forged. The From header is not authenticated by anything unless the domain publishes SPF and DKIM and enforces them with DMARC. Blocking a forged address blocks a string, not a person, and they'll use a different string tomorrow.
When you need a pattern rather than an address — an entire domain, a subject line, a header — use mail filters, which handle conditions the blocklist can't express. Filters are available on Pro and Agency.
One warning if you go that route: file into Junk rather than using discard. A discard rule is silent and permanent, and an over-broad condition destroys mail you needed without leaving a trace.
Rescuing Good Mail From Junk
The reverse case matters more, because a false positive costs you a customer and a false negative costs you five seconds.
Open the Junk folder, find the message, and use Not spam rather than dragging it out. Same asymmetry as before: dragging moves it, reporting teaches the classifier that mail like this is wanted.
If a sender's mail keeps landing in Junk despite repeated rescues, check two things. First, whether they're on your blocked senders list — an old block explains a lot, and it overrides everything the classifier has learned since. Second, whether the sender's own authentication is broken, which is the usual cause when a legitimate business consistently lands in spam for everyone rather than just you. That's their problem to fix, and why messages end up in spam covers what to send them.
Forwarded mail is a common special case. A message forwarded from another address arrives having failed the original sender's SPF check, which pushes it toward Junk through no fault of anyone involved. SRS repairs part of it automatically.
The Newsletter You Keep Blocking
Most of what people add to blocked senders isn't spam. It's mail they agreed to receive and no longer want: a newsletter from a shop, a product update, a conference mailing list.
Reporting that as spam is the wrong move, and it has a cost you don't see. Complaints are reported back to the sender through feedback loops, and a legitimate business that crosses a complaint threshold has its mail filtered for everyone, including the people who still want it. You've penalised a sender for a message you asked for.
Use the unsubscribe link. Every legitimate bulk sender is required to provide one under CAN-SPAM and equivalent rules elsewhere, and most mail clients surface it as a one-click button next to the sender name.
The rule of thumb: did I ever give them this address? If yes, unsubscribe. If no, report it as spam. If you unsubscribed and it kept coming, then report it — at that point it genuinely is spam.
A Playbook
| Situation | Do this |
|---|---|
| Obvious spam in your inbox | Report spam |
| Legitimate mail in Junk | Not spam |
| One person you don't want to hear from | Block sender |
| A newsletter you signed up for | Unsubscribe |
| An entire domain | A mail filter, not the blocklist |
| A rotating spam campaign | Report spam and let the classifier learn; blocking can't keep up |
| Something you're unsure about | Report spam — it's reversible, and discarding isn't |
And check your blocked senders list once a year. It accumulates addresses you blocked in a bad mood, and every one of them is mail you're silently not receiving.
Frequently Asked Questions
Does moving a message to Junk train the spam filter?
No. A folder move is only a folder move. Use Report spam, which moves the message and feeds it to the classifier as an example.
What's the difference between blocking a sender and reporting spam?
Reporting spam is a training signal that affects similar mail statistically. Blocked senders are an absolute override for one exact address, regardless of what the message contains.
Does the sender know I blocked them?
No. Nothing is bounced and no notification is sent. From their side the message was delivered normally.
How many blocked senders can I have?
Fifty per mailbox. If you're near that, the blocklist is the wrong tool — use a filter to match a pattern instead.
Can I block an entire domain?
Not with blocked senders, which match one exact address. A mail filter can match a domain, a subject or a header, and filters are available on Pro and Agency.
Is the spam filter shared across my team?
The statistical classifier is per mailbox, so your training doesn't change your colleague's results. Blocked senders are per mailbox too.
Why do a sender's messages still go to Junk after I marked them not spam?
Most often they're on your blocked senders list, which overrides the classifier. Otherwise the sender's own authentication is likely failing, which affects everyone who receives their mail.
Should I report a newsletter as spam?
Only if you never gave them your address, or you unsubscribed and it kept arriving. Otherwise use the unsubscribe link — spam complaints against a legitimate sender degrade their delivery for everyone.
