I use multiple email accounts with a volume of +100 emails a day, and web clients like gmail don't cut it for me, I need a desktop client to work. Thunderbird however just crawls, I've tried a million things but it just cannot handle that amount of email. Every morning I have to wait 10 seconds just for Thunderbird to load, then another 5 seconds until the folder I clicked on loads, then another 3 seconds until I finally get to read an email.

I've been looking for an alternative to Thunderbird for years now, but until now no dice. Here's what I'm after in a nutshell:

  • Not a fork of Mozilla Thunderbird
  • IMAP compatible
  • Fast, capable of handling large volumes of email without a sweat
  • In active development
  • Compatible with Windows 7
  • Advanced filtering (at least as feature-rich as Thunderbird's filters)

Is there such a thing?

  • Must it be free, or do you have a budget?
    – Mawg
    Commented Sep 28, 2015 at 14:45
  • 1
    @Mawg free and open source is prefered, since that way development can be picked up even if its author abandons it, but I'll take any suggestion :)
    – Mahn
    Commented Sep 28, 2015 at 15:41
  • Would it be you taking up the development? AFIAK, Thunderbird is FOSS .. go for it ,-) Or Eudora (remember that?) wiki.mozilla.org/Eudora_OSE But I see that you have accepted an answer, so let's leave it here. Glad you got a solution
    – Mawg
    Commented Sep 29, 2015 at 6:41
  • 1
    maybe Thunderbird gets so slow with that much messages because of the format (mbox) how messages are stored... for quite a while now Thunderbird offers an alternative (via advanced Settings) to store the messages in the maildir-format. - but keep in mind this setting gets only applied to new accounts, so you have to recreate existing ones to apply this setting to them. Commented Apr 26, 2018 at 13:45
  • If only there were a tool convert them :-(
    – Mawg
    Commented Aug 29, 2020 at 7:35

1 Answer 1


If you're looking for an email client that can handle a high volume of emails, then I would say Microsoft Outlook

Microsoft Outlook (Desktop not the web app)

  • Not a fork of Mozilla Thunderbird
  • IMAP compatible
  • Extremely Fast (The overall size of .pst and .ost files has a preconfigured limit of 50 GB. <- This can be increased too)
  • Always in Development
  • Compatible with Windows 7
  • Lots of filtering options

Outlook's Filtering Options

Outlook's User Interface

[Edit 1] @Mahn Does not want Outlook

I would then look into eM Client, I've this for quite some time before I switched back to outlook (only because it did not have PGP support, had it, I would have kept using) It also has an import feature that could import your Thunderbird profile. It's also quite fast, it doesn't take that long to startup and view emails.

eM Client (Free for personal use and one account)
eM Client is a Windows based email client, supporting calendars, contacts and tasks. It supports POP3 and IMAP4 servers as well as chat protocols (e.g. XMPP). Skype is supported as long as the user has installed Skype on the PC. Features:

  • Not a fork of Mozilla Thunderbird
  • IMAP compatible
  • Relatively fast
  • Currently in Development (Since 2007)
  • Compatible with Windows 7
  • Lot's of filtering options

EmClient's User Interface Background

  • 3
    I was kind of hoping for an alternative other than Outlook, but it's technically a valid suggestion.
    – Mahn
    Commented Jul 24, 2015 at 19:12
  • 3
    If your looking for an alternative to Thunderbird & Microsoft Outlook, then make sure you add it to your question.
    – Tom
    Commented Jul 24, 2015 at 19:24
  • 1
    You failed to mention that it's HTML support is as bad as Word. In fact, it uses the same rendering engine! Commented Jul 24, 2015 at 19:39
  • 3
    @Mahn Why not Outlook? Commented Jul 25, 2015 at 0:44
  • 2
    in my experience Outlook or Outlook express or Windows Live mail have not been good IMAP clients. eM Client is what I use and can recommend.
    – Adrien
    Commented May 27, 2016 at 10:09

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