Exporting email from Outlook and Gmail into an archive: step by step, without losses
From Save As to a finished ZIP with an index: how to pull messages out of Outlook and Gmail into formats the service accepts, and how to check that nothing went missing on the way.
What the service accepts — and what it does not
The service takes EML, MSG, MBOX and ZIPs containing them — plus PST and OST mailbox containers, which it unpacks into messages itself.
- Current limits are 1000 files and 500 MiB per upload, 50 MiB per file and a cap on ZIP expansion (1000 MiB and 2000 entries).
- The per-file cap applies to PST and OST too, so a large mailbox is easier to export as messages or folders.
- Plan around the limits so you do not repack the export three times.
Outlook: individual messages
Save one message as .eml: File → Save As, file type Outlook Message (.eml). The easiest way to create .msg is to drag: pull the message from your mailbox into a Windows folder and Outlook writes an MSG container.
- Both ways suit dozens of messages; for hundreds, exporting a whole folder is faster.
Outlook: a folder or the whole mailbox
A full mailbox export from the Import/Export wizard produces a PST, which the service reads directly and unpacks into messages.
- Mind the per-file cap: a large mailbox may not fit, and it is then easier to open it in Outlook and save the messages you need as EML or MSG, or export them with an application that writes EML or MBOX.
- Web Outlook hands data over through the Microsoft privacy dashboard; the contents and format of that export change over time, so inspect the files before uploading — the preflight inventory shows what was actually found.
Gmail: one by one and in bulk
For a single message: Show original → Download original message, which gives you an .eml with full headers.
- For a whole folder: Google Takeout, the Mail section, pick the labels — you receive an archive of MBOX files, usually one per label.
- Takeout is not instant: the link arrives by email, sometimes hours later, and a large mailbox may need a second attempt.
Pack the export into a ZIP
A ZIP is the neatest way to upload many messages at once: put the exported files inside and the folder structure is kept.
- Do not throw extra things in — anything that is not a message shows up in the report as unsupported.
- If the archive exceeds the limits, split the export into batches and process them one after another.
What you get back
One ZIP: a PDF for every processed message, attachments kept separately (compatible PDFs, images and TXT files can be appended into the message PDF itself), manifest.csv and manifest.xlsx indexes, an errors.csv report, a README and, optionally, checksums.
- A chronological merged PDF with a contents page can be ordered as an extra.
- Up to five messages a day are free; beyond that, credits are used.
How to verify that nothing was lost
Reconcile three numbers: what the preflight inventory found, how many rows the index has afterwards, and how many errors errors.csv lists.
- A gap is almost always explainable — duplicates, an unsupported format, a damaged file — and every reason is recorded in the report.
- Keep the source export and download the result before the one-hour access window ends: source files are deleted after packaging and the download link is short-lived.