How to Migrate from Postbox to Mailbird in 2026

A practical 2026 guide to moving from the retired Postbox email client to Mailbird, covering IMAP reconnection, POP and Local Folders, and how to verify mail before retiring Postbox.

Published on•
Last updated on•
13 min read
Christin Baumgarten

Operations Manager

Oliver Jackson
Reviewer

Email Marketing Specialist

Abraham Ranardo Sumarsono
Tester

Full Stack Engineer

Authored By Christin Baumgarten Operations Manager

Christin Baumgarten is the Operations Manager at Mailbird, where she drives product development and leads communications for this leading email client. With over a decade at Mailbird — from a marketing intern to Operations Manager — she offers deep expertise in email technology and productivity. Christin’s experience shaping product strategy and user engagement underscores her authority in the communication technology space.

Reviewed By Oliver Jackson Email Marketing Specialist

Oliver is an accomplished email marketing specialist with more than a decade's worth of experience. His strategic and creative approach to email campaigns has driven significant growth and engagement for businesses across diverse industries. A thought leader in his field, Oliver is known for his insightful webinars and guest posts, where he shares his expert knowledge. His unique blend of skill, creativity, and understanding of audience dynamics make him a standout in the realm of email marketing.

Tested By Abraham Ranardo Sumarsono Full Stack Engineer

Abraham Ranardo Sumarsono is a Full Stack Engineer at Mailbird, where he focuses on building reliable, user-friendly, and scalable solutions that enhance the email experience for thousands of users worldwide. With expertise in C# and .NET, he contributes across both front-end and back-end development, ensuring performance, security, and usability.

How to Migrate from Postbox to Mailbird in 2026
How to Migrate from Postbox to Mailbird in 2026

If you're looking for a Postbox alternative , this guide shows how to move from Postbox email to Mailbird without losing IMAP mail or older local archives.

To migrate from Postbox to Mailbird, treat IMAP accounts and local-only mail differently. IMAP-only moves are usually quick because the server already holds the messages. Older POP or Local Folders take longer because they need to be copied to IMAP first, and upload time depends on folder size and attachments. [2] [9]

What’s new

Postbox announced on October 22, 2024 that it would no longer be sold or developed, with support ending on December 22, 2024 and the Help Center remaining available until December 22, 2025. [1]

TL;DR

  • IMAP in Postbox: reconnect the same mailbox in Mailbird; no export is usually needed. [2] [10]
  • POP or Local Folders: upload that mail to IMAP first, then let Mailbird sync it. [4] [5] [9]
  • Backups matter: back up POP data and Local Folders before moving anything. [3] [4] [5] [13]
  • Verify before retiring Postbox: check each copied folder in webmail before you trust the move. [5] [9]
  • Skip the Import button: Mailbird’s direct import is for supported clients such as Thunderbird or Outlook, not for a direct Postbox import. [8]

Before you start

  • Prerequisites: a working Postbox install, Mailbird installed, every mailbox password, and webmail access for each account you plan to move.
  • What you'll need: your old Postbox profile, one IMAP mailbox with enough space, and enough time to let large folders upload fully.
  • Difficulty: easy if every account is already IMAP; moderate if you need to move POP or Local Folders. [2] [9]
  • Time: IMAP-only accounts are usually a single-session job; large local archives take longer because upload time grows with folder size and attachments. [9]
  • Safety notes: back up POP and Local Folders first, and do not delete a POP account until the same folders are visible in webmail and in Mailbird. POP mail is the risky part of this move because some or all of it may exist only on the old computer, so keep a backup until the IMAP copy is verified. [3] [4] [5] [13]

How to move from Postbox email to Mailbird: step by step

How to Migrate from Postbox to Mailbird in 2026

  1. Audit every Postbox account before you move anything

    Open Postbox account settings and make a simple list of each mailbox you care about: account name, IMAP or POP, and whether it has extra mail under Local Folders or On My Mac . If the account shows POP-only options such as leaving messages on the server, treat it as POP. Anything stored under Local Folders or On My Mac is local-only and needs its own copy step. [17] [3] [2]

  2. Back up local Postbox data first

    Quit Postbox completely. If you use POP or Local Folders, copy the mail data to a safe place before you change a single message. Confirm that the backup folder exists and contains mailbox files before reopening Postbox. [4] [5]

    Local Folders backup 
    macOS:~/Library/Application Support/PostboxApp/Profiles/your.profile/Mail/Local FoldersWindows:C:\Users\your-user-name\AppData\Roaming\PostboxApp\Profiles\your.profile\Mail\Local Folders
    POP account backup 
    macOS:~/Library/Application Support/PostboxApp/Profiles/your.profile/Mail/your POP accountWindows:C:\Users\your-user-name\AppData\Roaming\PostboxApp\Profiles\your.profile\Mail\your POP account

  3. Choose the IMAP mailbox that will hold the mail going forward

    If a mailbox is already IMAP, you can skip exporting it from Postbox because the server already holds the mail. If a mailbox is POP or local-only, create or choose an IMAP mailbox with enough storage, then add that IMAP account to Postbox now so it can receive the copied folders. [2] [4] [5]

  4. Put the source and target accounts in the same Postbox Account Group

    In Postbox, place the source account and the target IMAP account in the same Account Group so both folder trees stay visible. Rename them clearly—for example, Sales POP and Sales IMAP —before you start copying. Check that you can expand both accounts side by side without guessing which one is which. [5] [6]

  5. Copy Postbox mail into IMAP in small, checkable batches

    For Inbox, compare the POP or local source with the IMAP target and copy only the missing messages. For Sent and Archive, copy about 500 messages at a time. For Storage or Local folders, drag one whole folder at a time into the IMAP account, then wait until that copy finishes completely before touching the next folder. Do not send mail or start other cleanup while a large copy is running. [5]

  6. Verify the server copy before you move on

    After each batch or folder, compare message counts in Postbox and then sign in to webmail for the target IMAP account. If the folder and messages appear there, the server copy exists and Mailbird can sync it. If they do not, repeat the copy before moving to the next folder. [5] [9]

  7. Add the same IMAP account to Mailbird

    Open Mailbird account settings and add the same IMAP mailbox you just verified. In classic Mailbird, the path is Menu > Settings > Accounts > Add . For a Postbox move, use Mailbird's normal account setup, not its Import button: Mailbird's direct import is for a short list of supported clients such as Thunderbird, Outlook, Windows Live Mail, and IncrediMail. [10] [8]

  8. Fix provider sign-in requirements before retrying

    If Mailbird stops at sign-in, fix the provider requirement first and then retry the same account. Gmail or Google Workspace may need IMAP enabled. Outlook.com personal accounts may need IMAP turned on in Outlook on the web. Yahoo, AOL, and iCloud often need app passwords. Microsoft 365 mailboxes may need IMAP enabled by an admin before Mailbird can connect cleanly. [11] [14] [15]

  9. Let the first sync finish, then fix missing folders or slow sync

    If a folder is missing, check webmail first. If webmail has it but Postbox hides it, use File > Subscribe… or turn off Show only subscribed folders so you can confirm the folder is actually on IMAP. If Mailbird is slow or flaky during the initial pull, reduce the account's connection setting to 2, then 1 if needed. [7] [12]

  10. Retire Postbox only after everything matches

    Keep Postbox installed but read-only until every must-keep folder is visible in both Mailbird and webmail. If you later remove a POP account from Mailbird, make a backup first, because POP mail may exist only on the device. If you remove the old POP account from Postbox, do it only after the IMAP copy is complete and verified, and choose Yes if Postbox asks whether to save data. [3] [5] [13]

    If you use Mailbird on Windows, make a local Mailbird backup too: quit the app and copy C:\Users\ your-user-name \AppData\Local\Mailbird to a safe location. [13]

Why the Postbox-to-Mailbird method works

Mailbird syncs what exists on the IMAP server. Postbox says IMAP accounts do not need export, and Mailbird says direct import of offline folders into IMAP is not supported—but once those old local folders are uploaded to IMAP, Mailbird can sync them automatically. That turns a tricky client-to-client move into a cleaner server-backed switch to a modern desktop email client. [2] [8] [9]

Bottom line

For most users, migrating from Postbox to Mailbird is not an export project. If the account is already IMAP, add the same mailbox to Mailbird. If the mail still lives in POP or Local Folders, copy it to IMAP in Postbox first, verify it in webmail, and only then retire Postbox. [2] [5] [8] [9] [10]

Troubleshooting

  • Symptom Mailbird says “Nothing to import”
    Likely cause Mailbird could not detect a supported old-client profile, and Postbox is not on the direct-import list
    Fix Skip the Import button, add the account normally, and let IMAP sync the folders you already uploaded to the server. [8]

  • Symptom A folder exists in Postbox but not in Mailbird
    Likely cause The folder never made it to the IMAP server, or it is unsubscribed or hidden in Postbox
    Fix Check webmail first. If webmail has the folder, re-subscribe it in Postbox or turn off “Show only subscribed folders,” then wait for Mailbird to finish syncing. [7] [9]

  • Symptom Messages disappear after the switch
    Likely cause Another client is still using POP while Mailbird is using IMAP, or the old POP account is not leaving messages on the server
    Fix Stop using the POP client, turn on “Leave messages on server” where available, and re-upload any missing mail to IMAP before trusting the new setup. [18] [19]

  • Symptom Outlook.com or Hotmail will not sign in
    Likely cause Microsoft authentication changes or IMAP is disabled on the account
    Fix Install current Windows updates, enable IMAP in Outlook on the web, then remove and re-add the account in Mailbird. [15] [11]

  • Symptom Yahoo, AOL, or iCloud rejects the correct password
    Likely cause The provider expects an app-specific password instead of your normal login password
    Fix Create an app password with that provider and use it when adding the account to Mailbird. [11]

  • Symptom Mailbird sync is slow or keeps reconnecting
    Likely cause Too many simultaneous IMAP connections for that provider
    Fix Open the account settings in Mailbird and reduce connections to 2, then 1 if needed. [12]

  • Symptom You use Mailbird Next and your POP account will not add
    Likely cause The newer account-type flow is different from older Windows help articles
    Fix Upload the old mail to an IMAP account from Postbox first, then connect that IMAP account to Mailbird. [10] [16]

  • Symptom You removed an account and now worry about data loss
    Likely cause The account was removed before you had a verified backup or finished the IMAP copy
    Fix Restore from your Postbox or Mailbird backup, then reconnect through IMAP before deleting anything again. [5] [13]

Common Postbox-to-Mailbird scenarios

IMAP-only Postbox setup

This is the easy path. Do not export mail. Add the same account to Mailbird, let it sync, and verify the folders you already have on the server. [2] [10]

POP or Local Folders into the same mailbox

Add the IMAP version of that mailbox beside the old POP account in Postbox, copy Inbox, Sent, Archive, and Storage folders into IMAP, then connect the IMAP account to Mailbird. [5]

POP or Local Folders into a separate archive mailbox

If you do not want to mix old local mail into your everyday mailbox, create a separate IMAP archive account, upload the old folders there, and keep that archive account inside Mailbird as a second mailbox. [4] [6]

Windows bridge through Thunderbird

If you have already staged old Postbox archives in Thunderbird Local Folders, Mailbird can sync those folders after they are uploaded to IMAP, or import Thunderbird local folders into a POP3 account on supported Windows builds. [9] [8]

Large archives, storage, and switch-day prep

Make-ahead

Do the slow part first: upload old POP or Local folders to IMAP the night before, then leave only the Mailbird account setup and verification for your final switch session. [5] [9]

Storage

Keep one untouched copy of the original Postbox data until the same folders show up in both Mailbird and webmail. Those Postbox mailbox files are your fallback archive if you need to recover a missed folder later. [2] [4] [5]

Scaling

For large archives, move one folder at a time and compare counts after each copy. Postbox recommends waiting for each copy to complete, and Mailbird notes that upload time depends on folder size and attachments. [5] [9]

After the switch

If you also changed PCs, create a Mailbird data backup once the new setup is stable so you are not relying on a single live copy. [13]

Frequently Asked Questions

Can Mailbird import Postbox directly?

No. Mailbird does not offer a one-click Postbox importer. The normal path is to add the same IMAP account to Mailbird, or first copy Postbox local mail into IMAP and then sync it.

Sources: [8] [9]

Do I need to export IMAP mail from Postbox first?

No. If the account is already IMAP, the safer and simpler move is usually to add the same mailbox to Mailbird and let it sync from the server.

Sources: [2] [10]

What if my Postbox mail lives in POP or Local Folders?

Back it up first, copy it into an IMAP account from inside Postbox, verify it in webmail, and then connect that IMAP account to Mailbird.

Sources: [4] [5]

Will my folder structure move over?

Yes, if those folders are copied to the IMAP server first. If they remain local-only on the old computer, Mailbird cannot see them from the server side.

Sources: [3] [9]

Should I uninstall Postbox right away?

No. Keep it installed until every must-keep folder matches in Mailbird and in webmail, and until your backup is stored somewhere safe.

Sources: [5] [13]

Why are some folders missing in Mailbird?

Most often, the folder is not fully synced to the server yet, or it is unsubscribed or hidden in Postbox. Check webmail first, then Postbox subscription settings.

Sources: [7] [9]

What if Outlook.com or Hotmail won't connect after the move?

Enable IMAP in Outlook on the web, install current Windows updates, and then remove and re-add the account in Mailbird.

Sources: [15] [11]

Postbox to Mailbird checklist

Screenshot this and work top to bottom.

  • I listed every Postbox mailbox and marked it IMAP, POP, or Local.
  • I backed up all POP data and Local Folders before moving anything.
  • I chose an IMAP mailbox to hold all live and archived mail.
  • I copied old Postbox folders into IMAP in small, checked batches.
  • I verified each copied folder in webmail.
  • I added the same IMAP account to Mailbird instead of looking for a Postbox importer.
  • I fixed any IMAP, app-password, or Outlook sign-in requirements.
  • I checked for missing folders and subscription issues.
  • I kept Postbox read-only until Mailbird and webmail matched.
  • I saved a Mailbird backup on Windows after the switch.

What can change

Provider login rules and Mailbird menus change over time. Outlook.com and Hotmail authentication steps, and Mailbird Next account-type options, may look different from older Windows help articles. If a login screen or account-type option looks different on your device, verify the current Mailbird help article for your provider before you delete Postbox or any local backup. [10] [11] [15] [16]

To verify: check the folder in webmail first, then in Mailbird, and delete nothing until both match. [5] [9]

Sources

  1. Postbox blog: end of Postbox sales, development, and support (October 22, 2024)
  2. Postbox Support: How to Export Mail
  3. Postbox Support: A Guide to POP vs. IMAP
  4. Postbox Support: How to Create a Backup for Your POP or Local Folders
  5. Postbox Support: How to Convert a POP Account to IMAP
  6. Postbox Support: How to Move Messages and Folders
  7. Postbox Support: Subscribing to IMAP Folders
  8. Mailbird Support: How to Import Accounts and Emails to Mailbird
  9. Mailbird Support: How to import Local Folders from Thunderbird to Mailbird
  10. Mailbird Support: Connecting Accounts and Adding Identities in Mailbird
  11. Mailbird Support: How to enable IMAP for your email account in Mailbird
  12. Mailbird Support: Too many simultaneous connections
  13. Mailbird Support: How to backup your email data
  14. Mailbird Support: Server authentication failed
  15. Mailbird Support: Fix Microsoft Outlook / Hotmail Authentication Failures in Mailbird
  16. Mailbird Next Support: How to Check if Your Email Account Is Using IMAP or Exchange in Mailbird Next
  17. Postbox Support: Account Settings
  18. Mailbird Support: My emails get deleted or marked as read automatically
  19. Postbox Support: Leave Messages on Server (POP Accounts)