Which Email Providers Ignore Dots and Plus Tags

by EmailGuard Engineering

Unsplash

September 28, 2026engineering8 min read

Share this article

Enjoyed this article?

More notes on building products, infrastructure, and teams.

Gmail ignores dots in the local part. Proton Mail also treats dots, hyphens, and underscores as the same username. Outlook.com, Hotmail, Live, MSN, Fastmail, and iCloud lose a plus tag and keep their dots. A host outside that list, including Yahoo and a company domain, loses the plus tag and keeps the dots.

That is the built-in normalized string from detect email characteristics on 28 September 2026. Store the address the person typed. Put the unique index on normalized. The signup steps for that index are in how to normalize plus-addressed emails. This page is the host table that how-to left unnamed.

Plus tags are a provider choice. RFC 5233 describes the local+tag form for Sieve. It does not require every mail host to honor it.

The rules we ship

We ran the built-in normalizer on 28 September 2026. Domain case is folded. The local-part rules are per host.

Submitted	`normalized`	What changed
`jane.doe+news@gmail.com`	`janedoe@gmail.com`	Dots and plus tag
`jane.doe+news@googlemail.com`	`janedoe@googlemail.com`	Dots and plus tag. Domain stays `googlemail.com`
`Jane.Doe@Gmail.com`	`janedoe@gmail.com`	Dots only. `subaddressing` is still true
`jane_doe-x+tag@proton.me`	`janedoex@proton.me`	Plus tag, dots, `_`, `-`
`jane.doe+tag@outlook.com`	`jane.doe@outlook.com`	Plus tag. Dots stay
`jane.doe+tag@fastmail.com`	`jane.doe@fastmail.com`	Plus tag. Dots stay
`jane.doe+tag@icloud.com`	`jane.doe@icloud.com`	Plus tag. Dots stay
`jane.doe-shop@yahoo.com`	`jane.doe-shop@yahoo.com`	Nothing. Hyphen stays
`jane.doe+tag@yahoo.com`	`jane.doe@yahoo.com`	Plus tag, because Yahoo is not in the host table
`jane.doe+tag@acme.com`	`jane.doe@acme.com`	Plus tag. Dots stay

Hosts in each bucket:

Bucket	Hosts
Strip dots and a plus tag	`gmail.com`, `googlemail.com`
Strip dots, a plus tag, `-`, and `_`	`proton.me`, `protonmail.com`, `pm.me`, `protonmail.ch`
Strip a plus tag, keep dots	`outlook.com`, `hotmail.com`, `live.com`, `msn.com`, `fastmail.com`, `fastmail.fm`, `messagingengine.com`, `icloud.com`, `me.com`, `mac.com`
Not listed	Plus tag removed, dots kept. Yahoo lands here. So does `yourcompany.com`.

subaddressing is true when that rewrite changes the local part. A dotted Gmail address with no plus tag still sets it, because the dots came out. The flag means "this string was an alias of the normalized mailbox." It does not mean disposable. Read it next to subaddressing.

Gmail, and the Workspace exception

Google's help page on dots says a consumer Gmail address owns every dotted spelling of that username. The same page says dots do change the address when the mailbox is Gmail through work, school, or another organization, on a domain like yourdomain.com or yourschool.edu.

Our table follows that split. gmail.com and googlemail.com lose dots. jane@yourcompany.com does not, because that host is not in the Gmail row. It takes the fallback: plus tag off, dots left in place. jane.doe+tag@acme.com became jane.doe@acme.com in the run above.

googlemail.com is a legacy Gmail host. Delivery for the two domains is related. normalized does not rewrite one host into the other. jane@googlemail.com and jane@gmail.com are two strings. A unique index on normalized will not collapse them. If you need one row, fold googlemail.com to gmail.com in your own column after you read normalized.

Proton Mail

Proton's username help says ., _, and - are transparent. username, user_name, and user.name are one account, and a second account cannot take a variant. Their address help documents plus aliases such as ericnorbert+bills@proton.me as unlimited variations of an address you already have.

The Proton Key Transparency whitepaper states the same two steps for a Proton local part: if + is present, strip it and everything after it, then strip -, _, and .. That is the order our normalizer uses. jane_doe-x+tag@proton.me becomes janedoex@proton.me.

The four Proton hosts in the table are proton.me, protonmail.com, pm.me, and protonmail.ch. We do not fold those into a single domain. A custom domain hosted at Proton is not in the list, so it gets the fallback, not the Proton character strip.

One roundup of plus and dot tricks says Proton treats dots as significant, the same as Outlook and Yahoo. Proton's own username help says the opposite, and the normalizer follows Proton. If normalized on your account ever disagrees with this table, trust the API response. The table is the built-in set on 28 September 2026.

Outlook.com and Exchange Online

Microsoft's Outlook.com send-from page tells people they cannot sign in with the +sitename feature and cannot send mail that includes it. That is the consumer plus tag: receive-only, not a second mailbox you can log into.

Plus addressing in Exchange Online is on by default. The tag is not a mailbox alias. An organization can disable it. If inbound mail for an on-premises mailbox is not known to Exchange Online, Microsoft says plus addressing will not work there.

jane.doe+tag@outlook.com becomes jane.doe@outlook.com. Dots stay. The same plus-only rule covers hotmail.com, live.com, and msn.com. A Microsoft alias you create in account settings, with its own local part, is a different object. We do not invent that alias.

Fastmail

Fastmail's plus and subdomain addressing help says mail to alias+whatever@domain still arrives at the account. Subdomain addressing is the other form: whatever@alias.domain.

We strip the plus tag on fastmail.com, fastmail.fm, and messagingengine.com. Dots stay. normalized does not collapse subdomain addressing. shop@jane.fastmail.com is not rewritten to jane@fastmail.com. If you dedupe only on our field, that subdomain form remains a second key.

iCloud

We strip a plus tag on icloud.com, me.com, and mac.com, and we keep dots. jane.doe+tag@icloud.com becomes jane.doe@icloud.com.

Apple's iCloud Mail alias guide describes up to three @icloud.com aliases you create by hand. Hide My Email is a relay on a different host. On 28 September 2026 we did not find an Apple support page that documents an automatic +tag the way Google and Microsoft do. Treat the stripped iCloud string as our dedupe key. Send mail to the address the person typed.

Yahoo, and every other host

Yahoo's disposable-address help, fetched 28 September 2026, describes addresses you create as nickname-keyword@yahoo.com. You pick the nickname once. You add a keyword in settings. The page says it covers the old Yahoo Mail desktop help, and that the feature is for Yahoo Mail Plus subscribers and people who already have a nickname.

jane.doe-shop@yahoo.com stayed jane.doe-shop@yahoo.com in the run above. The hyphen is still there, so a Yahoo keyword address does not collapse into the base mailbox on normalized. Yahoo is also not in the host table, so the fallback removed the plus tag from jane.doe+tag@yahoo.com. That fallback is our rule for unlisted hosts. It is not a claim that Yahoo routes +tag mail.

The same fallback hit acme.com. Dots stayed, which matches Google's Workspace warning if acme.com is a work domain on Gmail. It can be the wrong merge if the mail admin disabled plus addressing, which Exchange Online allows. The original address is what you send to. normalized is the dedupe key, with that limit written down.

You can see the same rewrite without an API key on the email normalizer. Field names and the signup index are in the normalization knowledge base.

What to do with the string

Call detect on the server with a key that has email:detect.
Reject the row when syntax_validation is false, or when disposable is true. Alias rules are not a throwaway check. The block path is block disposable emails at signup.
Insert email as typed and email_normalized from normalized.
Unique-index email_normalized. On conflict, sign the person into the existing account or return your duplicate error.
If you also care about googlemail.com versus gmail.com, fold that host in your column. We do not.

Plans and quota for the detect call are on pricing.

FAQ

Which email providers ignore dots?

In our built-in rules, consumer gmail.com and googlemail.com ignore dots. Proton Mail hosts also drop dots, hyphens, and underscores: proton.me, protonmail.com, pm.me, and protonmail.ch. Outlook.com, Fastmail, iCloud, Yahoo, and company domains keep dots.

Does Gmail ignore dots on Google Workspace?

Google says no for work and school domains on your own hostname. Dots change that address. Our normalizer only strips dots on gmail.com and googlemail.com, so jane.doe@yourcompany.com stays dotted.

Does Proton ignore hyphens and underscores?

Yes, on the Proton hosts listed above. Proton's username help calls ., _, and - transparent, and a second account cannot register a variant. A custom domain on Proton is not in that list.

Should I strip plus tags on every domain myself?

You will miss Gmail dots and Proton's extra characters, and you will still have to decide what a company domain means. Read normalized from detect. Keep the typed address for mail and support.

Does `normalized` prove the mailbox accepts mail?

No. It is a canonical key for alias rules we maintain. It is not an SMTP probe. Yahoo's hyphen addresses and Fastmail subdomain addresses are two cases the key leaves alone on purpose.