I have three email accounts, Protonmail. gmail and hotmail. All are linked to my Thunderbird mail client and normally work correctly. However, occasionally I "loose" about 3-weeks worth of the Protonmail messages, they just disappear from Thunderbird. The messages are still present on the Protonmail server and I can see them from my cell phone, but I cannot get Thunderbird to download them again. This has happened a few times over several months. The only way I can get the missing messages to Thunderbird on my computer is to forward them to myself from my cell phone. New messages download as normal. Gmail and hotmail are not affected. The problem could be with Protonmail, but I don't think so. Thunderbird seems to "know" which messages have been downloaded and won't download them again. How can I force Thunderbird to download these missing messages? Thanks for any help. Thunderbird 102.8.0 32 bit on Windows 10 Home version 21H2