File Too Large to Email? Shrink It on Your Mac

Your mail service or your recipient’s mail server refused a message because the attachments added up to more than a cap. The caps below are the ones the providers publish on their own help pages. The limit that counts is the smaller of yours and theirs.

Outlook’s 20 MB is a default that a registry setting can change, and Microsoft’s page notes that the Exchange figure belongs to the administrator, so your own number may differ. Ask your IT provider if you are on a work mailbox.

The Gmail attachment limit is 25 MB on personal accounts. A 24 MB file can still bounce because mail is encoded for transport, which makes the message about 37% larger than the file on disk.

Our email PDF guide measured that overhead at 36.8% and turned it into a rule: divide the cap by 1.37. For a 25 MB cap, aim at 18 MB. When you do not know the recipient’s limit, aim at 7 MB, which clears the common defaults, including the 10 MB Exchange figure above.

For Outlook 2013 and later with a POP3 or IMAP account, Microsoft documents a default limit of 20 MB (20,480 KB), counting the sum of all attachments. On an Exchange mailbox the default is 10 MB, set by the administrator.

Both numbers are the sender’s side. The receiving server can refuse sooner, and you will not always know its cap. That is why the 7 MB target is useful for outgoing quotes and contracts: it clears all three sender limits in the table, so the file goes to a customer on any provider.

Drop the files into Smol, pick a PDF preset or a photo quality, run it, and read the output sizes before you attach anything. Smol sets quality and pixel size, not output bytes, so you check the result against your target.

1. 1

   Work out your target size

   Use 18 MB total for a 25 MB cap, 14 MB for a 20 MB cap, and 7 MB when you do not know the recipient’s limit.

2. 2

   Drag the files or the whole folder into Smol

   A PDF, a photo and a video can go in one batch. Smol writes a copy with a _compressed suffix beside each original and, by default, never overwrites the original.

3. 3

   Choose the setting for each type

   PDFs: preset Small. Photos: output JPG, quality 75. Video: MP4 with H.264 and a reduced resolution. The table below lists the starting points.

4. 4

   Run it and read the per-file sizes

   Smol shows each file’s size and the share saved. Add up the files you plan to attach. If the total is over your target, step down one preset or lower the quality.

5. 5

   Attach the compressed copies

   Open one compressed PDF and one photo first. If the text is readable and the image looks right, send them.

The PDF presets are pixel caps on the long edge (600, 900, 1200, 1800 and 2400 px for Tiny through Original), not DPI targets, so the saving depends on how the file was made. Our preset guide shows what each one does. The quality numbers for photos are our suggestions to start from. For HEIC, use Compress with output JPG; converting ignores the quality setting and writes a large file.

Compress it with the Small preset, check that the output is under your target, then attach it. If it is still too big, a scanned or image-heavy PDF may respond to Tiny, while a PDF with mostly text may barely shrink.

Results depend on how the PDF was made. Scans and files exported from design tools compress well. Files from some generators barely change, because there is little image data to remove. Our Gmail 25 MB walkthrough has measured examples with their conditions.

What if the PDF is a signed contract?

Compress first, then collect signatures. Compressing rewrites the file, so the signed copy is the one you should send unchanged. Smol does not sign, edit, merge or split PDFs, so keep your signing tool in the loop.

Do I have to send the attachment at all?

Not always. Gmail swaps an oversized attachment for a Drive link, and Apple Mail’s Mail Drop sends links for files up to 5 GB that expire after 30 days. A link works when the recipient is comfortable clicking one. An attachment is better for a customer who wants a file they can save and archive.

The free built-in options come first: your mail app’s link feature and Preview cover many cases. Smol covers the case where you need an actual smaller file in the attachment.

For a broader look at PDF tools, see the PDF compressor roundup. For the scanner end of the problem, the office scanning guide covers settings at the copier, and the sales decks page covers the PDFs you send prospects.

Solo is $29 once for one Mac. Team is $49 once for three Macs, managed from an admin dashboard. Enterprise is $20 per seat, once, for 5 to 500 seats. There is no subscription and no per-file limit.

A four-person office buys Team plus Solo, or five Enterprise seats. Presets live on each Mac, so write down the settings from the table above and recreate them on every machine. A Finder Quick Action puts Compress in the right-click menu. Pricing is on the buy page. There is no free trial, and purchases are not refundable.

• You need to send many gigabytes. Compression will not turn a 4 GB project into an attachment. Use a link, Mail Drop or a shared folder.
• The file must stay pixel-identical. Smol always re-encodes images and has no lossless mode. For that, a lossless optimizer fits better; see our ImageOptim head-to-head.
• The PDF has to be redacted, edited, signed or merged. Smol does none of these, and it does not run OCR.
• You are on Windows or a phone. Smol is a Mac app only.
• The attachment is already compact. A text-only PDF or a small photo may barely shrink, and if compressing would make a file larger, Smol keeps the original.