What is the maximum email attachment size?

It depends on the provider, but most consumer email caps a single message (including attachments) at 20–25 MB. Gmail and Yahoo say 25 MB; Outlook.com and iCloud Mail are 20 MB; ProtonMail is 25 MB; Fastmail is 70 MB; Microsoft 365 enterprise can go to 150 MB.

Why is the actual limit smaller than the advertised number?

Email encodes attachments as base64, which inflates binary data by about 37 %. So Gmail's '25 MB' really means about 18 MB of actual photo bytes once you account for encoding overhead, headers, and MIME boundaries.

What's a safe size to send to anyone?

About 14 MB of compressed binary data. That clears Outlook.com and iCloud Mail's 20 MB cap with margin and works on every other major provider too. EmailPhotos.com's default budget is 14 MB for this reason.

Can I send larger files via email?

Indirectly. Gmail and Apple Mail integrate cloud links automatically: Gmail uses Drive (up to 10 GB free), Apple Mail uses Mail Drop (up to 5 GB per email, 30-day expiry). Recipients click through to download instead of getting an attachment.

Email attachment size limits (2026)

Email attachment limits aren't what providers claim, and they vary in ways that matter when you're sending photos. Here's the current landscape, the math behind why it's not what's on the tin, and what to actually do about it.

The 2026 size limits at a glance

Provider	Advertised	Actual binary*	Cloud fallback
Gmail	25 MB send / 50 MB receive	~18 MB	Drive (15 GB free)
Outlook.com	20 MB	~14.5 MB	OneDrive prompt
Microsoft 365 (default)	33 MB	~24 MB	OneDrive (configurable to 150 MB)
iCloud Mail	20 MB	~14.5 MB	Mail Drop (5 GB, 30-day)
Yahoo Mail	25 MB	~18 MB	None
ProtonMail	25 MB	~18 MB	None
Fastmail	70 MB	~51 MB	None
Tutanota	25 MB	~18 MB	None

* Assumes ~37 % base64 + MIME overhead. Real-world headroom varies a couple of MB either way.

Why advertised limits aren't binary limits

The original 1982 email spec (RFC 822) and its 1996 MIME successor (RFC 2045) only allow ASCII text in the message body. Anything binary: a photo, a PDF, a spreadsheet: gets encoded as base64: every 3 bytes of binary become 4 ASCII characters. That's exactly 33.3 % expansion before you account for MIME framing, headers, and boundary markers, which add another 3–4 % in practice.

Combine that with the fact that providers measure the encoded message against their cap, not the raw photo bytes, and you get the common surprise: "the photo says 24 MB on disk but my email bounced at Gmail's 25 MB limit." After encoding, the message was closer to 33 MB.

The practical rule: divide the advertised limit by 1.37 to get the binary file size you can comfortably send.

The lowest-common-denominator number to remember

If you're emailing photos to "anyone, anywhere", the tightest cap in common use is Outlook.com's 20 MB advertised, ~14 MB actual. So target 14 MB as your binary attachment size and your email goes through to every major provider.

EmailPhotos.com defaults to a 14 MB budget for this reason, with two looser presets:

Gmail / Yahoo / Proton: 22 MB binary (~30 MB encoded fits the 25 MB cap with some slack? actually no: read the next paragraph).
Fastmail / Proton Plus: 45 MB binary (~62 MB encoded fits Fastmail's 70 MB cap).

Note: the 22 MB "Gmail" preset assumes you're targeting binary, with base64 expansion bringing the encoded message to ~30 MB: which actually exceeds Gmail's 25 MB hard cap. So 22 MB only works if you measure correctly. EmailPhotos.com does: it accounts for the overhead so the resulting email is under the provider limit.

What about provider-specific quirks?

Gmail

Receive limit (50 MB) is higher than send limit (25 MB). If a contact sends you a 40 MB attachment from Outlook, you'll get it. You won't be able to forward it without hitting the send limit.

Gmail's web compose offers automatic Drive integration for anything over 25 MB: your attachment becomes a "shared from Drive" link that recipients click to download.

iCloud Mail Drop

Apple's seamless workaround: any Mail.app attachment over 20 MB is silently uploaded to iCloud and replaced with a "click to download" link. Up to 5 GB per email. Recipients get 30 days to download. Doesn't work in third-party clients (Spark, Outlook for iOS, Gmail for iOS).

Outlook.com

Has a quirk where received messages can exceed 25 MB if they came in via a newer protocol; sent messages cap at 20 MB. Microsoft 365 enterprise admins can raise the cap to 150 MB.

Fastmail

Generously allows 70 MB per message. If both sender and recipient are on Fastmail, you can essentially attach a high-res photo album in one email.

What about videos?

Video bytes pile up fast. A typical 1080p iPhone clip is ~18 Mbps, so:

10 sec @ 1080p: ~22 MB. Tight at Gmail.
30 sec @ 1080p: ~66 MB. Way over.
1 min @ 1080p: ~130 MB. Cloud share territory.
1 min @ 720p re-encoded H.264 ~1.4 Mbps: ~10 MB. Fits comfortably.

EmailPhotos.com transcodes videos in your browser using WebCodecs, targeting 720p H.264 at a bitrate that fits your budget. For long clips that won't fit, the built-in trimmer lets you pick a 30-second highlight to send instead.

Best practices

Plan for 14 MB. If you don't know your recipient's provider, treat the limit as 14 MB binary.
Compress JPEGs to 1.5–2 MB each. Quality 0.8, 2560 px long edge: visually identical, fraction of the size.
Convert HEIC to JPEG. Outlook, Yahoo, Windows Mail can't open HEIC.
For 50+ photos, use a cloud link. Don't try to compress your way under 14 MB at the cost of quality.
Trim videos to ~30 s at 720p. Or share via Drive.