Check your anti-virus /firewalls http://kb.mozillazine.org/Firewalls

Yes I checked, disabled my Kaspersky Internet Security 13.0.1. But error still occurs.

In order for us to better investigate this issue you need to add a little more non-personal information.

Please add the troubleshooting information to your post To find the Troubleshooting information:

• Open Help (or click on three-line-icon and select Help)
• Choose Troubleshooting Information
• Use the button Copy to clipboard to select all. Do not check box "Include account names"!
• Paste this in your post.

Please also add the result of these troubleshooting steps to your post

• Does Thunderbird work in TB Safe mode (see Thunderbird Safe Mode)?
• Do you use anti-virus and firewall software? What is the version?
• Who is the email provider?
• Who is the internet provider?
• What is the exact error message?
• What steps did you take right before this happened?

Please post back with this information and any other questions you might have.

Uygulama temelleri

   Adı: Thunderbird
   Sürüm: 31.5.0
   Kullanıcı aracı: Mozilla/5.0 (Windows NT 6.2; WOW64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0
   Profil klasörü: Klasörü göster

             (Yerel sürücü)
   Uygulama Yapı No: 20150222233048
   Devredeki yan uygulamalar: about:plugins
   Yapılandırma: about:buildconfig
   Bellek kullanımı: about:memory

 Posta ve Haber Hesapları
   account1:
     INCOMING: account1, , (pop3) mail.mydomain.net:110, plain, passwordCleartext
     OUTGOING: mail.mydomain.net:587, plain, passwordCleartext, true

   account2:
     INCOMING: account2, , (none) Local Folders, plain, passwordCleartext

   account3:
     INCOMING: account3, , (pop3) mail.mydomain.net:110, plain, passwordCleartext
     OUTGOING: mail.mydomain.net:587, plain, passwordCleartext, true

   account4:
     INCOMING: account4, , (pop3) mail.mydomain.com:110, plain, passwordCleartext
     OUTGOING: mail.mydomain.com:587, plain, passwordCleartext, true

   account5:
     INCOMING: account5, , (pop3) pop.gmail.com:995, SSL, passwordCleartext
     OUTGOING: smtp.gmail.com:465, SSL, passwordCleartext, true

   account6:
     INCOMING: account6, , (pop3) pop3.live.com:995, SSL, passwordCleartext
     OUTGOING: smtp.live.com:465, SSL, passwordCleartext, true

   account8:
     INCOMING: account8, , (pop3) mail.mydomain.com:110, plain, passwordCleartext
     OUTGOING: mail.mydomain.com:587, plain, passwordCleartext, true

   account9:
     INCOMING: account9, , (pop3) mail.mydomain.com:110, plain, passwordCleartext
     OUTGOING: mail.mydomain.com:587, plain, passwordCleartext, true

 Crash Reports

 Eklentiler
   ImportExportTools, 3.1, true, {3ed8cc52-86fc-4613-9026-c1ef969da4c3}

 Değiştirilmiş önemli tercihler

   Adı: Değer

     browser.cache.disk.capacity: 358400
     browser.cache.disk.smart_size_cached_value: 358400
     browser.cache.disk.smart_size.first_run: false
     browser.cache.disk.smart_size.use_old_max: false
     extensions.lastAppVersion: 31.5.0
     font.internaluseonly.changed: false
     font.name.monospace.el: Consolas
     font.name.monospace.tr: Consolas
     font.name.monospace.x-baltic: Consolas
     font.name.monospace.x-central-euro: Consolas
     font.name.monospace.x-cyrillic: Consolas
     font.name.monospace.x-unicode: Consolas
     font.name.monospace.x-western: Consolas
     font.name.sans-serif.el: Calibri
     font.name.sans-serif.tr: Calibri
     font.name.sans-serif.x-baltic: Calibri
     font.name.sans-serif.x-central-euro: Calibri
     font.name.sans-serif.x-cyrillic: Calibri
     font.name.sans-serif.x-unicode: Calibri
     font.name.sans-serif.x-western: Calibri
     font.name.serif.el: Cambria
     font.name.serif.tr: Cambria
     font.name.serif.x-baltic: Cambria
     font.name.serif.x-central-euro: Cambria
     font.name.serif.x-cyrillic: Cambria
     font.name.serif.x-unicode: Cambria
     font.name.serif.x-western: Cambria
     font.size.fixed.el: 14
     font.size.fixed.tr: 14
     font.size.fixed.x-baltic: 14
     font.size.fixed.x-central-euro: 14
     font.size.fixed.x-cyrillic: 14
     font.size.fixed.x-unicode: 14
     font.size.fixed.x-western: 14
     font.size.variable.el: 17
     font.size.variable.tr: 17
     font.size.variable.x-baltic: 17
     font.size.variable.x-central-euro: 17
     font.size.variable.x-cyrillic: 17
     font.size.variable.x-unicode: 17
     font.size.variable.x-western: 17
     mail.openMessageBehavior.version: 1
     mailnews.database.global.datastore.id: 053887eb-f79e-40b9-94e0-9bebb74224c
     mailnews.database.global.views.conversation.columns: {"threadCol":{"visible":true,"ordinal":"1"},"flaggedCol":{"visible":true,"ordinal":"3"},"attachmentCol":{"visible":false…
     network.cookie.prefsMigrated: true
     places.database.lastMaintenance: 1426257722
     places.history.expiration.transient_current_max_pages: 104858
     plugin.importedState: true

 Çizimler

     Bağdaştırıcı açıklaması: Mobile Intel(R) 965 Express Chipset Family
     Satıcı kimliği: 0x8086
     Aygıt kimliği: 0x2a12
     Bağdaştırıcı RAM: Unknown
     Bağdaştırıcı sürücüleri: igdumd64 igd10umd64 igdumdx32 igd10umd32
     Sürücü sürümü: 8.15.10.1930
     Sürücü tarihi: 9-23-2009
     Direct2D etkin: Grafik kartı sürücüsü sürümünüz için engellenmiştir.
     DirectWrite etkin değil: false (6.2.9200.16581)
     ClearType parametreleri: ClearType parametreleri bulunamadı
     WebGL çizici: false
     Grafik ivmelendirilmiş pencereler: 2/2 Direct3D 9

     AzureCanvasBackend: skia
     AzureSkiaAccelerated: 0
     AzureFallbackCanvasBackend: cairo
     AzureContentBackend: cairo

 JavaScript

 Artırımlı GC: 1

 Erişilebilirlik

   Etkinleştirildi: 0
   Erişilebilirliği engelle: 0

 Kitaplık sürümleri

     Beklenen minimum sürüm
     Kullanılan sürüm

     NSPR
     4.10.6
     4.10.6

     NSS
     3.16.2.3 Basic ECC
     3.16.2.3 Basic ECC

     NSS Util
     3.16.2.3
     3.16.2.3

     NSS SSL
     3.16.2.3 Basic ECC
     3.16.2.3 Basic ECC

     NSS S/MIME
     3.16.2.3 Basic ECC
     3.16.2.3 Basic ECC

As you can see I have 9 accounts. I changed my own mails as mail.mydomain.com. Athough I have problem with other accounts sometimes, there are no error now. I have problem only with Hotmail (account6) now.

   Does Thunderbird work in TB Safe mode (see Thunderbird Safe Mode)?

No, it is not safe mode now. I confirmed. I also tried with TB Safe mode, there is no change.

   Do you use anti-virus and firewall software? What is the version?

I use Kaspersky Internet Security 13.0.1 as Antivirus and Firewall. Although I had disabled it, problem occured again.

   Who is the email provider?

Hotmail

   Who is the internet provider?

Vodafone TR

   What is the exact error message?

Turkish: "İletinin gönderilmesi başarısız. İleti gönderilemedi çünkü smtp.live.com SMTP sunucusuna bağlanma girişimi başarısız oldu. Sunucu hizmet dışı ya da SMTP bağlantılarını reddediyor olabilir. Lütfen SMTP sunucunuzun ayarlarının doğru olduğunu teyit edip yeniden deneyin veya sunucu yöneticinizle görüşün." English: "The message could not be sent because connecting to SMTP server smtp.live.com failed. The server may be unavailable or is refusing SMTP connections. Please verify that your SMTP server setting is correct and try again, or else contact your network administrator."

   What steps did you take right before this happened? 

I dont remember, but as I said before, it occurs sometimes not always.

PS: When I got this error once, I connected to my VPN server, and then it could connect SMTP and send successfully. I am trying same method now, connecting same VPN server, but still can not connect to SMTP .

Is it smtp.live.com that doesnt send? Try this:

smtp.live.com / 587 / TLS

Authentication same as POP3 (username and password)

Thanks very much!

I changed port from 465 to 587; and Connection Security: STARTTLS

Everything is ok now.