Case will be handle case-by-case and it depends on intensity for rule violation as well as each moderator perspective when applying forum's (un)official rules.
Usually, sending unsolicited PMs will cause to 7-day temporary ban (first offence), 14-day temporary ban (second offence) but like the following case, it's 30-day temporary ban for a first offence.
You sent over 100 PMs with the same format: clear unsolicited bulk PMs. 4 people reported it, making it unwanted & unsolicited bulk PMs = spam. Most others would've been banned much longer.