SUMMARY
Kmail creates a conflict with the audio that you hear disturbed and out of sync if you use HDMI audio output. If I close Kmail the audio returns to normal. The problem only occurs with the HDMI output.
Hardware in desktop use with Amd Radeon R5 230 graphics
The problem has occurred for a long time both on Tumleweed.
Below are the hardware features.
A greeting.

STEPS TO REPRODUCE
1. start kmail
2. audio disturbed and out of sync
3. stop kmail the audio returns to normal
OBSERVED RESULT


EXPECTED RESULT


SOFTWARE/OS VERSIONS
Windows: 
MacOS: 
Linux/KDE Plasma: Tumbleweed - Leap 15 - Kde Neon
(available in About System)
KDE Plasma Version: 5.4.13
KDE Frameworks Version: 5.52.0
Qt Version: 5.11.2

ADDITIONAL INFORMATION
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System:    Host: linux-9w7x Kernel: 4.19.4-1-default x86_64 bits: 64 
           Desktop: KDE Plasma 5.14.3 Distro: openSUSE Tumbleweed 20181126 
Machine:   Type: Laptop System: Acer product: Aspire E1-522 v: V2.09 serial: <filter> 
           Mobo: Acer model: Aspire E1-522 v: V2.09 serial: <filter> UEFI: Insyde v: 2.09 
           date: 11/19/2013 
Battery:   ID-1: BAT0 charge: 28.0 Wh condition: 28.0/37.0 Wh (76%) 
CPU:       Topology: Quad Core model: AMD E2-3800 APU with Radeon HD Graphics bits: 64 
           type: MCP L2 cache: 2048 KiB 
           Speed: 879 MHz min/max: 800/1300 MHz Core speeds (MHz): 1: 879 2: 809 3: 831 
           4: 820 
Graphics:  Device-1: AMD Kabini [Radeon HD 8280 / R3 Series] driver: radeon v: kernel 
           Display: x11 server: X.org 1.20.3 driver: ati,radeon 
           unloaded: fbdev,modesetting,vesa resolution: <xdpyinfo missing> 
           OpenGL: renderer: AMD KABINI (DRM 2.50.0 4.19.4-1-default LLVM 6.0.1) 
           v: 4.5 Mesa 18.1.7 
Audio:     Device-1: AMD Kabini HDMI/DP Audio driver: snd_hda_intel 
           Device-2: AMD FCH Azalia driver: snd_hda_intel 
           Sound Server: ALSA v: k4.19.4-1-default 
Network:   Device-1: Qualcomm Atheros QCA8171 Gigabit Ethernet driver: alx 
           IF: enp1s0f0 state: down mac: <filter> 
           Device-2: Qualcomm Atheros QCA9565 / AR9565 Wireless Network Adapter 
           driver: ath9k 
           IF: wlp5s0 state: up mac: <filter> 
           Device-3: Lite-On Atheros AR3012 Bluetooth type: USB driver: btusb 
Drives:    Local Storage: total: 111.79 GiB used: 23.00 GiB (20.6%) 
           ID-1: /dev/sda vendor: Kingston model: SV300S37A120G size: 111.79 GiB 
Partition: ID-1: / size: 50.01 GiB used: 6.89 GiB (13.8%) fs: btrfs dev: /dev/sda2 
           ID-2: /home size: 58.97 GiB used: 16.10 GiB (27.3%) fs: xfs dev: /dev/sda3 
           ID-3: /opt size: 50.01 GiB used: 6.89 GiB (13.8%) fs: btrfs dev: /dev/sda2 
           ID-4: /tmp size: 50.01 GiB used: 6.89 GiB (13.8%) fs: btrfs dev: /dev/sda2 
           ID-5: /var size: 50.01 GiB used: 6.89 GiB (13.8%) fs: btrfs dev: /dev/sda2 
Sensors:   System Temperatures: cpu: 64.0 C mobo: N/A gpu: radeon temp: 65 C 
           Fan Speeds (RPM): N/A 
Info:      Processes: 235 Uptime: 3h 27m Memory: 7.24 GiB used: 3.29 GiB (45.5%) 
           Shell: bash inxi: 3.0.27