This issue still persists in 4.52. Every time I click the check/send mail button the handles count increases by 6 and the thread count by 1. Checking with Process Explorer it shows me, that on each click it adds 4 unnamed event handles and 2 thread handles to the newly created thread. The trace of the threads, that are being leaked are looking like this:

ntoskrnl.exe!IoIs32bitProcess+0x25

ntoskrnl.exe!FsRtlAddBaseMcbEntry+0x82

ntoskrnl.exe!FsRtlInsertPerStreamContext+0x48e

ntoskrnl.exe!_snwprintf+0x1c

ntoskrnl.exe!KeInitializeQueue+0x3b

ntoskrnl.exe!KeDelayExecutionThread+0x1c7

ntoskrnl.exe!FsRtlInsertPerStreamContext+0x48e

ntoskrnl.exe!SePrivilegeObjectAuditAlarm+0x240f

ntoskrnl.exe!MmFreeContiguousMemory+0x90d

wow64cpu.dll+0x42d9

wow64cpu.dll+0x40e5

ntdll.dll+0x1c846

kernel32.dll+0x18c0d

ws2_32.dll+0xd0b7

kernel32.dll+0x1fe37

I had some speed issues with my machine today and checked a few processes for memory, handle, thread etc. usage and recognised, that my Pegasus Mail was using 126 threads. I restarted it to check, if it was really needing that much and saw it had just 3 threads on the initial start-up I tried some basic functionality and found out, that the leak occurs every time I check my POP3. It doesn't seem to depend on how much accounts you check (I got 2, but also tried it with one disabled), but on the check itself.

Update: It also leaks when I send a mail. 

[quote user="Kidman"]

I had some speed issues with my machine today and checked a few processes for memory, handle, thread etc. usage and recognised, that my Pegasus Mail was using 126 threads. I restarted it to check, if it was really needing that much and saw it had just 3 threads on the initial start-up I tried some basic functionality and found out, that the leak occurs every time I check my POP3. It doesn't seem to depend on how much accounts you check (I got 2, but also tried it with one disabled), but on the check itself.

Update: It also leaks when I send a mail. 

[/quote]

Perhaps it's little comfort, but I suspect those are (merely) thread handles and not actual threads.  PM leaks a lot of handles.  That will probably get better when the switch from the Borland development tools to MS VC is made.
 

[quote user="Kidman"]

I had some speed issues with my machine today and checked a few processes for memory, handle, thread etc. usage and recognised, that my Pegasus Mail was using 126 threads. I restarted it to check, if it was really needing that much and saw it had just 3 threads on the initial start-up I tried some basic functionality and found out, that the leak occurs every time I check my POP3. It doesn't seem to depend on how much accounts you check (I got 2, but also tried it with one disabled), but on the check itself.

Update: It also leaks when I send a mail. 

[/quote]

Just FYI : This is forwarded to the attention of the beta team.